I’ve read reviews of happy users that were using the scale down version of Ubuntu known as Ubuntu Netbook Remix on their netbooks. Most people who have tried to use the full fledge Ubuntu Desktop (meant to be run on PCs and Laptops) were having display issues on their netbooks since the fact is that netbooks have a smaller screen size.
You can get Ubuntu Netbook Remix here. Again, it’s free 🙂
More info here