My wife just got an 11" MacBook Air, so I am setting her old computer up for my Sister-in-Law. I did a clean install of 12.04 LTS. The machine has 2 GB RAM, so I stayed with the 32 bit version, although this computer will support the 64 bit version. It has the AMD Athlon(tm) Neo Processor MV-40.
I installed with a separate /home partition following these instructions.
So far everything has worked flawlessly. I installed Ubuntu Restricted Extras, lame, GnuCash, Asunder, Weather Indicator and that's about it. Setting up WiFi was as simple as plugging in the password (WPA2).
One thing that I did notice was that I didn't have to install GPointing Device Settings to get the TrackPoint to work. Scrolling worked right out of the box.
Comparing the appearance to OS X, and even some of the set-up procedure, it's plain to see that they took some cues from Mac. That may bother some folks, but just like OS X, Ubuntu has a distinctive look and way of doing things.
Any questions, let me know.