To all who are wondering if this trip is worth it I can only say DEFINITELY. But be prepared to become addicted. I had no previous dive experience with pellagic travelers so I was a little nervous. However, once you see all those hammerheads (and others) for the first time, you just want to get back in and see them again. The boat ride is not that bad, except on the way back it's a little depressing because you know you are coming back to reality. We are going back in November and I am already counting down the days.
Choppersrule - there is never any certainty on any given day that you will see the big schools. There were definitely a few sites (Alcyone, Dirty Rock) where there was more action. However, after a great show at Alcyone one day, the next day there were hardly any HHs. So, it all depends. Recently they have been seeing lots of whalesharks. We only saw one (and I missed it). The DMs told us that in Jan / Feb sometimes they will only see a handful of HHs the entire week.