I have a Netbook and used Wubi to make it a dual boot. So I have both Windows XP and ubuntu desktop. I like the flexibility of having both.
IMO Ubuntu is great for using a Netbook just to browse the web. My GUI install came with Firefox.
However, there can be media compatability licensing issues. I don't think it's possible to stream Netflix in Ubuntu(because it requires Microsoft Silverlight). MP3 also seemed to have licensing issues but I think there are work arounds for it. So if you're managing music files it could be a minor annoyance.