This thread was inspired by comments in another unrelated thread about dissappointment with the slow boats at Cozumel.
My wife and I went to Cozumel for the first time a few years ago, after we were already very experienced divers (she's a PADI instructor and I'm a DM). When we got down there, we asked to dive on the fast boats and they said they were already booked for the week (we found out later that it wasn't quite true), so we got stuck on the sloooooow boats. We ended up diving the same sites 2 and 3 days in a row because they took a "vote" and my wife and I kept getting out voted. We also couldn't believe some of the jerks who were all over the reef, yanking critters out of holes and generally going through like a wrecking crew, with no interference from the the DM's :11: . When we left for home we were very disappointed, and felt like we had just wasted a week of vacation. We wrote a nasty letter to Dive Paradise, and sent a copy of it to our LDS (we both used to work there and the owners and staff are friends). Scott (one of the owners) then contacted DP, as he has sent a LOT of business to Dive Paradise over the years).
Anyway, Dive Paradise ended up sending us a certificate for a free week of diving in their EDP (Experienced Diver Program, 50 logged dives were required) on the six-pack fast boats. It's the only thing that could have gotten us back to Coz after the lousy experience. It was a lot better, and we dove well away from the masses for most of that week, dove the farther out reefs like Maracaibo and Palancar, and had a pretty decent, if not spectacular, week. I still doubt that we will go back, as there are too many better diving destinations and not enough time to see them all, but at least we learned something. Now we always ask for a small boat up front when booking. If the operator doesn't offer it, we look someplace else.
Cozumel is still a good, economical place to go, especially for the less experienced diver, but there are things to watch out for, and I recommend avoiding the cattle boats if at all possible.