Just returned 11/24 from Akumal. We stayed at the Bahia Pricipe Resort (which I thought was a fabulous value BTW), and my wife doesn't dive; so it wasn't really a dive trip for me. I almost didn't bring gear, but decided to at the last minute just in case I could get her into a resort Discover Diving class or something. Glad I did.
We used Bahia Divers because they're on the property and they were very good as well. They probably cost a little more than Hidden Worlds because they're on-site; but they let me tag along on my wife's lesson & ocean dive for the cost of a tank of air. Really nice guys, free gear lockers in the dive shack, warm showers on the beach.
Viz in ocean off Akumal was still pretty bad in the wake of H.Wilma (like 20 feet!), so we booked a Cenote dive as well and that was wonderful! (Actually she snorkeled above while I dove below because you have to be cert'd to go in the cenotes.)
Crystal clear, all-fresh water in Dos Ojos, 72 degrees, viz limited only by the power of your dive lite. Fantastic experience, like flying around with all the stalagtites and columns and stuff. 3mm long wetsuit highly recommended, maybe even a hood would be nice in case you bump your head.
We got plenty far in on marked trails with a guide. I only have 12 dives, but had no reason to be scared. Buoyancy control is important, but the trails are clearly lined out, and usually in at least 8' - 10' of water. We never went deeper than 30', so we could come out, swap tanks and keep going without surface time.
I would highly recommend the experience for any divers in the area. It's a great "intro to cave diving"!