If you are getting a netbook and are using it strictly for surfing the web and email, then Linux would be fine. The learning curve with Ubuntu is pretty easy, and there are so many things you can add-on easily. I have it on a dual boot on my work laptop, but because we are a Microsoft shop, I'm booted into XP 99% of the time.
I was looking at the Dell Mini 12 as well, but I'm now leaning towards this
MSI Wind from Newegg to be my new personal portable computer, from which I will probably do a dual boot XP Home/Ubuntu, maybe even add OSX to the mix.
And OpenOffice is a great alternative to MS Office. I've used it interchangeably with Office 2007 for a while now, and with the things I use it for, users haven't noticed any difference.