Recently I bought my wife an Acer Aspire One as a gift. It came preloaded with Windows XP SP3, but of course I found this unacceptable. It seems a little silly to load a six year OS on a brand new PC. So, I opted to download and install Windows 7 Beta. As you may or may not know the Aspire One does not include a built in CD drive so your only option is to do an install from either an external hard drive or a USB thumbdrive, HERE are some instructions if you need to know how to do that.
The installation went off without a hitch and Win 7 found drivers for everything but the wifi card a little poking around on the net and I found THIS SITE. After installing the driver manually and a reboot everything worked fine. After using my network to install some apps and join the mini to my AD domain the mini notebook works like a champ. Even with 1 GB of ram and the Atom processor the system is surprisingly fast and stable. Able to run multiple apps and switch back and fourth with no issue.
My one criticism is that the tiny keyboard and touchpad take some getting used to but what do you expect for such a small size. Overall I am very impressed and Microsoft is true to their word. Windows 7 is truly notebook and netbook friendly. If you have an Aspire One I strongly encourage you to give Windows 7 a try.