Amazon (AMZN) launched a new service called Amazon Video on Demand, which allows users, for a fee, to watch any of 40,000 TV episodes or movies, in real time, on their Windows and Macintosh computers, and on specially equipped Sony Bravia TV sets. This service replaces an earlier Amazon video offering called Unbox.

I have been testing Amazon Video on Demand and I found it worked well, although it has some limitations. The user interface is clean and smart, the quality is good if you have a fast Internet connection, and there are some clever features. On the downside, it works poorly with the slow connections typical in places like hotels. And there are some studio-imposed limits on what content is offered and how you can view it.

To date, there have been three major models for legally getting TV shows and movies from the Web.

In one, best represented by Apple’s (AAPL) widely used iTunes store, the TV shows and movies are ad-free, but you pay for each. All of this content is downloaded to your Windows or Macintosh computer or your Apple TV set-top box for later viewing, even when you’re not connected to the Internet — though on Apple TV you can start watching while the material is being downloaded.

A second model, best represented by the studio-owned Hulu.com, presents movies and TV shows on a Windows or Macintosh personal computer free of charge, but requires you to watch commercials that can’t be skipped. The TV shows and movies you view on Hulu are “streamed” rather than downloaded, meaning they are meant to be viewed immediately, in real time, rather than stored for viewing when you’re not connected to the Internet.

The third online model is best represented by Netflix (NFLX), the popular DVD distributor. It offers a “Watch Instantly” streaming option on Windows PCs or on TVs equipped with a special set-top box, for a small portion of its large catalog of TV shows and movies. These videos are ad-free and don’t carry an individual charge, but require a monthly subscription fee.

The new Amazon Video on Demand service is a hybrid of these others. As on iTunes, the TV shows and movies it offers are ad-free and purchased individually, don’t require a subscription, and work on both Windows and the Mac, plus on one type of set-top box. In Amazon’s case, that’s Sony’s Bravia Internet Link, a $299 device that works only with Sony (SNE) TVs.

But, like Hulu and Netflix and unlike Amazon’s older Unbox service, the new Amazon Video on Demand service offers videos via real-time streaming. In many cases, it also allows downloading, iTunes-style, to Windows PCs (but not Macs) and to TiVo devices attached to a TV. The videos can’t be streamed in real time using a TiVo (TIVO).

Amazon’s streaming videos are viewed in any of the major Web browsers and don’t require any special software. I tested the new service on both Windows PCs and Macs, and on a Sony Bravia TV equipped with the $299 adapter box. In my tests, Amazon’s videos looked quite good over a fast Internet connection. However, on a typically lousy hotel Internet connection, the movies were often grainy and kept stuttering.

The new service doesn’t yet offer videos in high definition, something Apple just announced this week it is adding for some TV shows. Amazon says it is working on HD.

Amazon’s user interface for the new service is very nice. All of your purchased videos are available in a library stored on the company’s servers, so you can easily watch them again and again if they are purchased, or resume a partly watched rental. And the service remembers where you stopped watching a video and resumes it at that point, even if you started it on, say, a Dell (DELL), and resumed it on a Mac.

On the downside, the new Amazon service isn’t always simple or consistent. For instance, you can watch only two videos at a time, and not all titles can be either streamed and downloaded, or be either purchased or rented. Most rentals last 24 hours, but some differ.

Selection was OK, but not great. Because of studio policies, many current and recent movie hits aren’t available. There are gaps as well in the TV selection. For example, while iTunes offers the current second season of the excellent “Mad Men” series, Amazon has only the first season.

Prices also can be confusing. Amazon rents most movies for $3.99 and sells them for between $9.99 and $14.99. TV shows generally cost $1.99. But some titles carry different prices, albeit these are often lower.

All in all, Amazon Video on Demand is a good service for people who prefer paying for ad-free TV shows and movies, and is another strong step in the Internet’s rising competition with traditional TV.

Find all of Walt Mossberg’s columns and videos online, free, at the All Things Digital Web site, walt.allthingsd.com. Email him at mossberg@wsj.com.

But there’s more than one way to get a strong, fast Internet signal all over your house. You aren’t limited to using a single wireless router. You don’t have to install a bunch of complicated wireless “range extenders.” And you don’t have to snake networking cables through your walls.

Instead, there’s a simple alternative that’s often overlooked: Using small gadgets called Powerline adapters, you can route your Internet connection around your house over your regular electrical power lines, the ones already in your walls. It really works, it’s fast and it doesn’t disrupt your electrical system. Even better, it requires zero technical skill.

You just plug one of the adapters into a standard electrical outlet near the place where your Internet connection enters your home. Then, you connect the adapter to your wired or wireless router. Next, you plug a second, identical adapter into an electrical outlet in a distant room where you lack an Internet connection. Finally, you plug a computer (or even a wireless access point) into that second adapter. There’s no setup, no required software and no technicians or tools are needed.

When you plug in a computer into the second Powerline adapter, it’s as if that computer was right next to your cable or DSL modem and router. You are on the Internet at full speed. If you plug a Wi-Fi wireless access point into the second Powerline adapter, it will create a wireless network in and around the distant room, which multiple computers can use.

I first reviewed these Powerline adapters in 2003. I liked them, but they were a little slow and never took off. Now, however, one of the leading home network product makers, Netgear, offers a whole line of faster Powerline adapters.

I’ve been testing one of Netgear’s newest models, the XE104, which costs $100 per adapter, and I can heartily recommend it. It couldn’t be simpler or more effective. In my tests, the XE104 gave me wicked-fast connections. I tried plugging Windows and Macintosh laptops directly into the adapters in rooms where my wireless signal was weakest. I also tried plugging a Wi-Fi wireless access point into an XE104 adapter and picking up the connection wirelessly on the laptops. (An access point is a wireless gadget that takes a wired Internet connection and propagates it through the air.)

In all scenarios, the Netgear XE104 adapters delivered nearly the full speed of my Internet service, which in my case is very fast — 15 megabits per second downstream and two mbps upstream. In fact, the XE104 can handle speeds up to 85 mbps, far faster than any common connection.

You can use up to four Netgear adapters at once, and the company claims they will cover a 5,000-square-foot home. Netgear includes optional software to encrypt your Powerline connection, but this is needed only if you share an electrical system with other families.

Linksys, Belkin and other companies also make Powerline adapters, sometimes called bridges. But Netgear is the leader in this category, and I didn’t test the other brands.

The XE104 is a small, white rectangular gadget about 4 inches high, 3 inches wide and 1.5 inches thick. It carries a standard two-pronged electrical plug and mounts right into the wall outlet.

On the side, there are four standard Ethernet network ports, like the kind on your router and laptop. Netgear includes a short Ethernet cable so you can connect the first adapter to your router and the second one to a PC or a wireless access point.

The four Ethernet ports are what make the XE104 a “switch.” They allow you to connect each adapter to multiple devices. For instance, the first adapter can be connected both to your router and to a PC. The second might be connected to a PC, a wireless access point and a device like a game console.

Netgear makes a similar model without the multiple Ethernet ports, called the XE103, for $80. There’s also a costlier model that goes up to 200 mbps, though that’s overkill for 99% of people.

The company also makes a Powerline adapter with a built-in wireless access point for the distant room, the $150 WGXB102 model. This saves you the cost and hassle of buying and connecting a separate access point. But it’s slower and uses older technology. In my tests, it was less than half as fast as using the XE104 with a separate, modern wireless access point.

Unfortunately, like a lot of network-equipment makers, Netgear is clueless about naming products so that normal humans can understand what they are. The XE104 is officially called the XE104 85 Mbps Wall-Plugged Ethernet Switch. That’s like calling a table lamp the LS482 75 Watt Wall-Plugged Switched Illumination Device.

Netgear even makes it hard to find the XE104 on its Web site, netgear.com. It lists it under a section called “Bridges, Access Points, and Range Extenders.” You can buy them at computer stores and other retail outlets.

These adapters are a terrific way to clear up Internet dead spots.

• Email me at mossberg@wsj.com.