It's playing great here too, I have the cheapest iMac model currently available here; I believe it's got 4GB RAM and not the fastest processor but no hitches at all. I only got it 2 weeks ago though, so real problems would've been unlikely.
Loved the DVD, by the way. Pulled it out of the post box late at night, after a long and intense meeting for the upcoming Redhead Days but I popped it into my SuperDrive right away. Quite a lovely compilation of footage you got there, it really gave a nice insight into the process. If I missed anything, it would be a blooper reel. You shared some great bloopers in your older videos and they totally cracked me up so some goofs would've been nice but other than that: great!