I did this...it took a little elbow grease but it was worth it in the end. I ended up with a "10 inch Macbook" for $330 (including Snow Leopard).
Overall I think the keyboard (as mentioned) takes some getting adjusted to, and the tiny trackpad is a little difficult. But for on the quick websurfing and simple document work you can't beat it.
http://gizmodo.com/5389166/how-to-ha...eopard-netbook