I run it on an MSI Wind U100 netbook. Despite all the issues it runs better than Windows XP on the machine - only slightly better though.
I have had a few annoying issues:
- When I boot up the netbook the brightness applet gets stuck in an infinite loop and increasing and decreasing the brightness. The screen flashes like it is 1999

- Getting my HSDPA 3G USB modem to work reliably is almost impossible. Plug it in and no option to connet in Network Manager. Unplug and plug in and the option is there. Try to connect and it won't. Try 10 times and it won't. Then it connects. Reloaded XP and it works fine. Go to Ubuntu and it doesn't. Incredibly annoying!
I am really starting to believe that they should move their release cycle to 12 months instead of 6. When you look at the number of bugs that get ignored due to them rushing to get the release out you can see why some people have issues. Get the quality right and then worry about new features
That said I still enjoy running Ubuntu on the netbook and so I hope they can bump up the quality. And all the posts (okay maybe one or two) I am reading on planet.ubuntu.com basically trashing people who had problems with the install and "debunking the myth of the broken ubuntu" aren't helping. If something is broken and some arrogant person starts chirping you for it you aren't going to be very happy/inclined to stay with the OS.