As Driftwood said, the biggest problem is getting to the reef. We were in the area (Xcalak) last spring for a week. It was never good enough for a trip, but in fairness the tides were the most extreme in years, and a Norte was sweeping the area. We went with no expectations of being able to make it to the reef, so weren't disappointed when we didn't. We did have great diving in the area, boat picked us up at our resort, 5 or 10 minute ride out over the reef, we were the only people at any particular spot, reefs in great shape, tons of diverse marine life. Did our dive, went back to resort for SI, boat showed up hour or so later with fresh tanks for another round to a different spot. The diving is very similar to Ambergris Caye which is only a short distance away, basically slots in the reef which is 20-40 ft and drop down to 40-80 ft. Very cool diving. We used an op out of Xcalak and had no problems. I don't know anything about the op you mentioned other then what is on the net.
It is a remote spot, literally the end of the road, but is not all that hard to get to. At least I didn't think so. You can't fly in directly, step off a plane and be at your resort, but it's not a major expedition. We rented a car in Playa del Carmen after a week on Cozumel, picked up some groceries, drove down in a few hours, stayed a week, and dropped the car off in Cancun on our way out of Mexico. There are some logistical concerns like gas and grocery avalibility, no atms or banks, but nothing you can't get wrapped around with a little planning.
Just an FYI in case you don't know, but Mahaual was pretty much leveled during Hurricane Dean last summer. It wiped out the cruise ship piers and port along with most everything else in the port proper. I'm not sure what the situation is now. Through some fluke in storm positioning, atmospheric conditions and Karma, most of Xcalak and the surrounding area were spared all but minor damage.
