I looked at them briefly, thinking I could take a Dell Mini & Hackintosh it but after I saw one first hand I couldn't bear the thought of being so cramped. (I don't even have large hands, I swear!) Found a good deal on a 13" MacBook and couldn't be happier.
I suppose if you're looking to travel really light and can accept the limitations in screen size, storage and lack of expandability then they're certainly cheap enough.