Using IDEs with netbook is not really good experience: screen area is just too small for having all components on screen same time and you cannot help noticing that modern IDEs do need way too much resources to be smooth on such tiny machine. Netbooks cannot really be used like normal laptops: usually there is no other option than programs fullscreen, which in practise means you need virtual desktops. This effectively throws windows to the bin, but if that is not problem for you.. go ahead and get one. Just make sure you test it beforehand, many netbooks still have horrible keyboards!

Lately I have been doing most of my developing on netbook using vim and must say I love it. There is no performance problems with any scripting languages, not even while having mysql + rails/cakephp on. Only problem is compiling bigger projects when doing c/c++, but that isn't problem if you have access to box with more power like you suggested.

My own machine is Samsung n140, although my config is not the most usual one: stripped down arch + xmonad. Battery life while using wlan is from 10 to 14 hours. The reason why I ended to this particular machine is combination of awesome battery life + really nice keyboard, one of the best I have found from any laptop. Minus side is kinda low quality HDD which blew up quite fast, but I use this machine only on battery power with agressive spindowning and load count jumps into sky fast which can explain.