- The wireless driver worked, but it's range and speed was much less than under OS X. For example, sitting on the couch in my living room I got 4 bars with OS X but just two bars with Ubuntu. (Now, of course, the two operating systems could be reporting the same information in different ways. But actual network activities OS X seems faster and more reliable.)
- The connectivity to Windows file shares is much more reliable. With Ubuntu I could not reliably use VLC to play AVI movies off of a Windows Vista file share. The AVI movies would always timeout sometime in the first few minutes of play. With OS X I have no problem.
- I couldn't figure out how to get suspend and resume to work right in Ubuntu. As a result, battery life was not as good.
- The trackpad never felt good. And a single-button computer will always be a second-class citizen in Linux.
- The Linux UI experience wasn't as solid. (The fit and finish, and how much flickering went on.)
- The UI quality of add-on applications was somewhat lacking. And the use of three or four different UI widget sets was downright confusing. To be fair, OS X and Vista have issues with this as well, but in OS X and Vista the issue is a generational one, while in Linux the issue is a civil war: there are three competing UI widget sets.
So it's back to OS X for me, for now.