I live here, have my own boat (see my avatar for a pic), dive a lot, and know the local shops.
Scubatech is a credible operation. They run a boat called the Sea Cobra. It is a converted head boat and some would call it a "cattle boat" since it will hold a bunch of people.
They dive sites within ~8 miles of the pass, most of which are reasonable dives, but all "on schedule." Their trips tend to be 4 hours, half-day, $50 or so for two dives, figure 20-25 minutes each with a 1 hour SI between. Where they go depends on local conditions on any given day. I've been on their boat and they did my original cert. In the summer, with enough demand, they will also do a single night dive. They DO expect you to have real open water experience or they will insist you hire a DM for the trip at significant extra cost - probably good on their part, as most of the sites they dive are in the 80' range for the first, and 60-70' for the second of the trip, and as such they're considered "advanced". Than again most diving in Destin is! The shop banks EANx32 and Air, and if Steve is there you can get custom EANx mixes provided they're not too insanely busy.
I know the folks who run the place reasonably well, and if this is the kind of diving you're looking for, they're a good choice.
Emerald Coast Scuba (ECS) runs charters as well. They are a BIT looser with their schedule, tend to plan more ahead (that is, they don't do the "two runs every day" thing), do some longer offshore trips (more expensive though) and their boat holds fewer people. I have not dove with them, but I DO see their boat out on the water quite a bit. The people there are nice and I've never heard anyone say bad things about them - but no direct experience to back it up on my part. As of my last contact with them a few months ago they continuous blended and filled straight from the compressor - no banks. They said they were going to be installing them, however, and were planning a major expansion. No idea how far along any of that is.
There are two other local shops that I'm aware of; one is more local-oriented and doesn't run much in the way of charters that I've heard if any at all, although he (Chuck's) does have a decent selection of gear and such and also has a Nitrox membrane system, and I know next to nothing about the 4th operation - been in there a couple of times, but that's it.
There are also lots of people who just plain dive. Like me, for instance. There is a somewhat-loose-association of divers who keep a mailing list for our trips (BWBDivers@yahoogroups.com.) I post my intended runs when I have room on board among my friends; anyone who is on the list and wants to come is welcome.
Note that none of us are charter operators! What this means is that you're just diving with a bunch of people who happen to be on a boat, and one of them owns the boat. In other words, diving with friends .vs. diving for money. Trips can be significantly more intense in terms of the diving (for instance, I typically dive sits in 100-120' of water for the first of the day, sometimes as deep as 100' on the second, and if we do a third it might be in 70-80'), we all tend to dive Nitrox, and on my boat at least most of us will be spearfishing. There is no fixed schedule among most of us, of course, other than when everyone needs to be home. Most of us (myself included) typically split fuel (before someone chimes in, this is perfectly legal - the charter guys may not like it, but the law says its kosher to voluntarily contribute to the actual costs of a recreational boating trip.) Gear carried and the boat itself varies depending on who's it is - mine is a midsize sportfish, and is quite a bit more "yacht" than "workboat" (e.g. it has a real galley, head, and A/C in the cabin!) Nobody will hold your hand when among friends, of course, and you'd be wise to match yourself pretty carefully against the planned itinerary - some of the folks around here are pretty much "look around at the pretty fish" people, and then there are folks like me who would like to EAT the fish
(The only problem with this is that sometimes the man in the gray suit shows up, and he has at least a passing thought of perhaps eating YOU!)
Bring a buddy if you're diving with locals, or talk with them for a while first, because if they're the spearing kind of folks they may be effectively solo, even if they're a "buddy in name", and where folks are going and how intense they are with their diving varies WIDELY.
PM me if you'd like to know more privately, or blast away here... I know the local diving area reasonably well (20-25nm from the Destin pass) out to the ~120-130' depth range, and fish this area pretty heavily also. The diving here can be very nice, especially if you get beyond the "cattle boat" range (LOTS fewer people both fishing AND diving those sites!) but you have to be comfortable with it, whether you decide to get on a charter operation's run or find locals to blow some bubbles with.
