I have an inspiron 1720. Its tollerable most of the time but can often slow massively for no good reason, even after a fresh installation of window. That said, its taken some abuse and still works.
I use acers at work and they perform well enough but are flimsy; I wouldnt trust them to last.
Apparently sony and asus are the best around. So, Asus, then, since I loathe sony.