Just got back from ACEP (damn you, Medicine sub-I)...
If you have the money and time, I would recommend anybody who's going to be a 4th year to go next year... it's a good opportunity to schmooze and it's pretty fun.
The medical student sessions were fair... went over very basic stuff. The most important thing I got out of it was that, yes, plain white shirts are the way to go. But, it definitely wasn't useful for 3rd years, and maybe even marginally useful for a lot of 4th years.
The best thing about this was the residency fair. First you get to show your face to all your away rotations folks. Next, you really get to check out programs you're interested in... I was surprised at how much one-on-one face time I got with PDs... even the most coveted programs had empty tables for periods of time... I pretty much just popped into empty tables most of the time and still hit almost all of the places I was planning to. I think I may have bought myself 1-3 interviews just by chatting with people there.
I'm just bummed that I had to come back so soon to finish up my inpatient sub-I... so sad.