Dove with them before, but not in Maldives, in Egypt. Was a good experience. As everywhere it is down to the individual DM/Guide more than the operation. In the Maldives in general, operations tend to be in very good shape as far as the equipment/training of their DMs goes. Diving is pretty high price and it shows. Very safety conscious and they will get you out of the water after 60 mins (National Park rules) and enforce the 30m depth limit.
Do not worry about cattle boats. The Maldives island resorts are generally small, not everyone dives and you are likely to have a max of 10-15 divers on your boat. When I last went to a resort island there, there were never more than 10 divers on the boat per trip and they limited the dive group size to 5 + guide/DM. Which is nice as most of it is drift diving and they usually require to keep the group together - so no swanning of with your buddy.