When it comes to laptops, ultrathin is in -- particularly since the launch of Apple's MacBook Air earlier this year. As might be expected, though, the Air isn't the only game in town -- skinny laptops are available from a variety of other vendors.

However, stylish doesn't always mean functional. You needn't look further than the latest style in women's shoes to know that what looks good isn't necessarily comfortable. Is the MacBook Air with its ultrasvelte shape actually as comfortable to use as larger, more traditionally shaped laptops? And, come to that, what about its competitors? How easy are they to use?

Note that we're not talking about the low-cost ultraportable laptops like the Asus Eee and Everex CloudBook. These laptops are larger and more full-featured. For instance, that new breed of ultraportables has, at most, 10-in. displays, while the smallest display in this group was 12.1 inches. However, they also contain a number of compromises (such as tweaked keyboards or less ports) that could affect the user experience.

To find out how these thin notebooks really rate, we asked the usability experts at Perceptive Sciences, a US-based user experience testing firm, to run the Air and two Windows-based ultrathin laptops -- the Lenovo ThinkPad X300 and the Toshiba Portege R500-S5002-- through a gamut of hands-on tests with 20 independent users.

So how does the much-ballyhooed MacBook Air stack up against its competitors? Here's what we learned.

Air and its competitors

Before we get to the results, a few words are in order about the laptops themselves and how we tested them.

Apple's MacBook Air has garnered a lot of publicity since its introduction in January, largely because of how thin it is -- at its thickest point it's a scant .76 inches thick. Weighing in at three pounds, the Air might be easy to carry, but it is comparatively powerful, with a 13.3-in. display and an Intel 1.6-MHz Core 2 Duo processor and an 80GB hard drive.

Although they haven't received the level of attention that the MacBook has, the skinny offerings from Toshiba and Lenovo have been well reviewed as well. The Lenovo ThinkPad X300, which was introduced in February 2008, is slightly lighter but also slightly thicker than Apple's offering and has the same size display as the Air. The review unit had a 1.2-GHz Core 2 Duo processor and, uniquely for this group, a 64GB solid-state drive.

Toshiba's Portege R500-S5002 has a particular emphasis on lightness. At 2.4 pounds, the company has been claiming it is the world's lightest full laptop. The trade-off is in screen size; at 12.1 inches, the R500 has the smallest display in this group. Like the Lenovo, this laptop came with a 1.2-GHz Core 2 Duo processor. It also had a standard 120GB hard drive. (We were told after testing began that the Portege R500-S5002 has been discontinued; however, a Toshiba representative assured us that the size of the current model, the Portege R500-S5006V, which comes with a 160GB hard drive and a 1.33-GHz processor, is the same.)