Unfortunately, every attempt at this concept has included too many compromises to justify their often surprisingly high prices. I’ve been testing the latest effort at such a device, the Eee PC, from a Taiwan-based laptop maker called Asus. It does better than some of the earlier contenders in certain respects, such as text entry and price. But it still is likely to prove unsatisfying for many road warriors.

Asus doesn’t even call the Eee a computer, referring to it as a “mobile Internet gadget.” Instead of using Microsoft Windows as its operating system, the Eee uses a specially designed version of the open Linux operating system, and comes preloaded with a variety of open-source programs for Web browsing, performing office tasks, playing music and videos, running games and managing photos.

The Eee has a much smaller footprint than even the subnotebook category of laptop, such as the much-publicized MacBook Air unveiled by Apple this week (which I’ll review after I have thoroughly tested it), or subnotebooks from Sony and Lenovo. It weighs a mere two pounds, is just under 9 inches wide and just over 6 inches deep. It is thicker than the new Apple and some other subnotebooks, ranging from 0.79 inches at its thinnest point to 1.26 inches at its thickest. The overall effect is small, but stubby.

The Eee’s price is only a fraction of what typical subnotebooks cost — from $300 to $500, depending on configuration. The model I tested, called the Surf, is the base $300 entry. With its pastel blue lid, and tiny size, it looks like something Barbie might use. But it can perform real work, even though it comes with only 512 megabytes of memory and a scant two gigabytes of storage space.

One reason the device costs and weighs so little is that there is no hard disk. Files are stored on memory chips. It is possible to add storage by popping in a flash memory card or by connecting a USB drive to one of the three USB ports.

Unlike some computers in its category, the Eee isn’t a tablet. It takes the clamshell form of a traditional laptop and, when opened, reveals a full, if very cramped, keyboard. By including a real keyboard and charging so little, Asus has overcome two of the problems that plagued Samsung’s Q1 ultramobile computer awhile back.

Asus Eee PC

The user interface on the Eee is simple and clear. It consists of tabs labeled Internet, Work, Learn, Play, Settings and Favorites. Each tab contains large, colorful icons. For instance, the Work tab includes icons for Documents, Spreadsheets and Presentations. These tabs lead to various modules of the free OpenOffice suite, a competitor to Microsoft Office.

The Internet tab has various icons, such as Web Mail, Web and Wikipedia, that open the Firefox Web browser. You get to this tabbed screen by just pressing a Home button.

In my tests of the Eee, I was able to use all manner of Web sites, send and receive Web-based email, compose and open Microsoft Word documents from other computers, play music, and view photos.

So, with a low price, a small size, a real keyboard, and a clean user interface, what’s not to like about the Eee?

Well, for starters, its tiny 7-inch display is just too stingy for serious work. You can make up for a small screen size with high resolution, but the 800 by 480 resolution on the Eee — which can’t be changed — is so wimpy that very few lines of text can be seen at any one time. This means you’ll have to do so much scrolling, it’s likely to drive you crazy.

Also, the lack of a hard disk, and the relative paucity of truly simple Linux software, means that most nontechie users will be stuck with the included programs, which can’t be removed and which don’t include a calendar or contacts program, or even an email program. You can only use Web-based email.

And just below the Eee’s simplified user interface lurks the complicated terminology and software design characteristic of Linux. Some error messages I saw were indecipherable.

Beyond that, many of the Linux programs included were far cruder and harder to figure out than, say, Microsoft’s Photo Gallery or Apple’s iTunes. The Eee wouldn’t automatically reconnect to a known wireless network, and it wouldn’t recognize my Kodak digital camera.

Some of these problems can be solved if you install Microsoft Windows XP on the Eee. Asus includes instructions on doing so. But you have to supply your own copy of Windows.

The Eee is a valiant effort, but it still has too many compromises to pry most travelers away from their larger laptops.

Email me at mossberg@wsj.com. Find all my columns and videos online, free, at the new All Things Digital Web site, http://walt.allthingsd.com.

So, last year, when Samsung introduced a new class of tiny Windows computer called the Ultra-Mobile PC, I gave it a harsh review and advised waiting for an improved model. That first effort, the Q1, was spurned by consumers, despite the high hopes of Microsoft and Intel, which conceived the UMPC.

But Samsung now has come up with a much better version, called the Q1 Ultra, which will go on sale at major electronics stores starting next month.

I’ve been testing the Q1 Ultra and, at least for certain classes of users, I believe it’s a pretty good product, despite some lingering downsides and compromises. It addresses the biggest weaknesses of its predecessor and throws in other improvements, yet starts at a significantly lower price — $799 compared with $1,099 for the original Q1.

The biggest improvement: Even though the Ultra is a tablet computer, still able to accept handwritten notes and meant to be controlled by a stylus, this new model now has a built-in keyboard. It’s just a tiny BlackBerry-style keyboard but it makes writing emails and typing in Web addresses practical.

The Samsung UMPC still isn’t a mainstream product, or one that I’d recommend for most average users. It does run the full version of Windows Vista or Windows XP, but it’s still too compromised to replace a small laptop for most folks.

However, I do see the Q1 Ultra as a decent choice for people willing to put up with some limitations in return for the ability to carry a real Windows computer that is as small as a thin hardcover book and weighs almost nothing. These users include students and frequent business travelers who mainly want to take notes, write emails, do instant messaging and Web surfing, and play music and videos. For people who want to do a lot of word processing, or to create spreadsheets or presentations, it would be better to stick to a small laptop.

The Q1 Ultra is a sleek, shiny, black tablet with a bright, sharp seven-inch screen that feels great in the hand and has a built-in stand on the back so it can be used upright. It weighs about 1.5 pounds, is less than nine inches long and five inches wide, and is under an inch thick. It’s slightly smaller and lighter than last year’s model.

The Q1 Ultra is run by a special, low-horsepower Intel processor and has only one gigabyte of memory, which can’t be expanded. But it runs Vista acceptably, if not exactly speedily. You can get one with Windows XP for faster performance.

Samsung’s Q1 Ultra

The main flaws in the first model were a high price, the lack of a keyboard, a screen that had too little resolution to manage Windows, weak battery life, no built-in mouse buttons and no built-in cellphone modem to augment its built-in Wi-Fi wireless networking.

In the new Ultra model, the built-in keyboard, meant for thumb typing, is split, with half of the keys on either side of the screen. This approach looks daunting, but works pretty well once you get the hang of it. Unfortunately, Samsung and Microsoft didn’t build any intelligence into this keyboard, so it doesn’t automatically complete words, add punctuation and capitalize the first letters of sentences, unlike the keyboards on most smart phones.

While still the same size, the screen is both brighter and has a higher resolution, so open windows can be easily moved and closed. There are now mouse buttons and an optional internal high-speed cellphone modem is available. The navigation pad is simpler and is easily programmable, though you have to manually set its arrow keys to mimic the arrows on a real keyboard.

Alas, the battery-life problems remain. In my tests, where I turn off all power-saving software, use maximum screen brightness, turn on the Wi-Fi and play an endless loop of music, the standard battery lasted just two hours and five minutes, which translates to about three hours in more normal usage. The $99 optional extra-large battery, which adds a little bulk and weight, did only about 50% better.

And this little computer can still be pricey. The base model is $799, but there are three better-equipped models that can range up to $1,499. That’s almost as much as a tiny Fujitsu tablet with a regular keyboard, and way above Microsoft’s $500 target price for the UMPC.

Another big problem is start-up time. Even with no programs running, it took me over four minutes to reboot the Q1 Ultra and over two minutes to boot it after a complete shutdown. To speed up start times, Samsung suggests either turning off Vista’s snazzy graphics or ordering the one model with Windows XP, which costs $1,149.

Still, if you don’t do a lot of document creation, and value small size and weight enough to put up with some hassles, the UMPC finally is an acceptable choice.

• Email me at mossberg@wsj.com. Find all my columns and videos online free at the new All Things Digital Web site, http://walt.allthingsd.com.