I've got some Macs these days, but I'm still a vi kind of guy. It's what I do pretty much all my work in, as far as work that involves editing text goes. It had always driven me a little crazy, though, that when I was using vi in iTerm (which is an excellent terminal emulator for Mac OS X - I highly recommend it), if I copied text from elsewhere and pasted it in, if you pasted in a line that went over the width of the terminal, it would break the long line up into many little lines and generally never worked right.
While I was setting up my new Mac and futzing about with it in general, I stuck in a USB flash drive that had been formatted with ext3. Needless to say it didn't mount it or anything, and I removed it shortly after. I then noticed that if I moused over the notifier area in the upper right corner of the screen (where the date, volume, Time Machine, etc. controls are), the Spinning Rainbow Ball of Doom showed up.