Hi Alex.
I picked Cobalt based on reviews posted on Scubaboard.com and a few other travel sites. I haven't stayed anywhere else so I can't make comparisons to other resorts/hotels. The location was nice - it's a about a 13 minute drive from town so it's pretty quiet - no cruiselines. The food was good, but the menu is limited. However, they were accommodating (changing spices, medium/well done etc.). The staff is very accommodating of divers' needs. The rooms were nice (suite with a bedroom, living room, minfridge, and bathroom. There's a TV in the bedroom and the living room. Beds were comfortable and rooms were nicely air conditioned)but the cleaning staff was on the lazy side.
The on location dive op was great and offered a variety of classes and trips (diving from boat, shore; night dives, scooter dives, various classes, etc.). Most of the dives are off the North wall (best diving from what I've read), but we did visit the West side once or twice. They also have a "house reef" - it's a short swim from their pier to a reef where I
saw squid, turtles, stingrays and other animals/fish.
I own all my dive and picture taking equipment except for a reg/octo set-up. I rented that and tanks and weights were included in the package. The water was about 84-86 degrees at the surface and a 3 mil was plenty!
If I return to Grand Cayman I'd most likely book with them again.