Mobility Guru compared the Toshiba Libretto U100-S213 with the Sony VAIO VGN-TX670P, Dell Latitude X1 and the Fujitsu LifeBook F1510D.
The Toshiba Libretto U100-S213 is one of world's smallest notebooks - measuring only 8.27" x 1.31" x 6.50" (21.0 x 3.33 x 16.51 cm). The notebook weighs 2.2 pounds (1kg) and features a 7.2" widescreen with a 1280 x 768 resolution. Don't expect a lot of performance from these notebooks, they are more aimed at bringing extreme portability
Toshiba's Libretto U100-S213 is a very nicely built, ultra lightweight laptop with lots of features and very good battery life. It suffers from some limitations due to its small size, including a small keyboard and keys, use of a joystick instead of a touchpad and such a small screen that it's difficult to read very sharp fonts when the display is set for optimal resolution. If you can live with these limitations and you want a laptop that isn't all that far from being a PDA, the U100 could be just the answer for you.