I've been running Ubuntu Netbook Remix on my 1st generation Acer Aspire One (the one with 512MB RAM and 8GB flash storage) since shortly after it was released. It has been running well enough that I'm considering getting another netbook running Linux with a bit more hardware resources. Dell's Inspiron mini models have the option to be shipped with Ubuntu (but not UNR). Dell provides a look at what's shipping on netbooks and notebooks with Ubuntu 9.04 in this blog item...

Ubuntu Linux 9.04 - Technical Details

Dell provides Ubuntu 9.04 with Cyberlink PowerDVD (for notebooks with DVD drives). They also created a graphical tool for media recovery. Dell also notes that all Dell branded wireless cards are natively supported by Ubuntu 9.04.

You can find more information about Dell's Ubuntu 9.04 implementation on the...

Dell Ubuntu 9.04 wiki page