I think this is a great question. First off some speakers are good, some presentations are good, and some topics are good. But sometimes the info isn't very useful or is just boring.
Some videos are posted for free (very few) so check out those on the homepage of IMAC www.theimac.org.
Otherwise... for 2004 that was the Boston fiasco. If you are paying full retail price, I'd probably not purchase the $170 set but just a few you are interested in. (www.bostonreefers.org) I'm struggling to remember what topics each of those presenters discussed. My suggestions would be... Debelius, Jackson, Knop, Riddle, Veron, Yaiullo. I'd have to see the schedule again to give better advise because I really can't remember the topics.
Adam