The Asus Eee is half the size of a 12.1"; widescreen notebook like the Toshiba Portégé R400.

This is one of the first budget ultra-portable PCs to go on sale, but expect to see more devices like this even without the extremes of the crank-powered OLPC. Via has a reference design for a cheap ultra-portable that will be the same size and weight as the Eee PC, but it will have a 1.2-GHz VIA C7 CPU, a VX-700 chipset, up to 1GB of RAM, Bluetooth and Wi-Fi connectivity, a DVI port and a 4-in-1 card reader.

The question is how useful these systems will be. They’re far better equipped for Web browsing and email than a smartphone but a better comparison is an intermediate device like the HTC Advantage, which comes with Opera and the Office Mobile apps in Windows Mobile 6 that rival OpenOffice.Org, includes GPS and has a better battery life.

The Eee only looks thick because it’s so small; it’s a thin as an ultra-portable tablet like the Toshiba R400.

One big advantage of the is being able to connect standard peripherals. Either Linux or Windows XP is a far more capable operating system than any of the alternatives, but the limited storage means you can’t install as many applications as you might want. Performance isn’t the limitation you might expect, but the cramped keyboard may prove the real stumbling block. Nevertheless, the combination of size, price and sturdiness make this a real step forward for anyone who wants to carry a PC around without being weighed down.