The problem is the screen. 600x1024 is the bare minimum. I use an Acer Aspire One, which is a great netbook, very responsive, runs everything I throw at it at decent, if not breathtaking, speeds, but the screen is the weakest point. When on a desk, I always hook it up to a desktop monitor.

Unfortunately, the Intel GMA driver is buggy (https://bugs.launchpad.net/ubuntu/+bug/302227). Annoying but functional.