CRD is certainly among the best of the ops in that area, perhaps the top dog service and friendly-wise. I've been lucky to have gone out with about 15 operators between Tavernier and K.L. over the years, most still around but some no longer among the living. When I've shown up as a loner at CRD they've always been extremely friendly and welcoming. I've been to a couple of other ops in the area (highly regarded ops here on SB) that have sometimes been less than enthusiastic about a single revenue customer showing up at their door. And Brenda has the ability to recognize a long absent face or telephone voice when you walk in. (Joe at Ocean Divers is also good that way; he oughta be a politician.) I've never been on any of the CRD boats when they were in the cattle boat mode but I suppose it can happen, just like on any larger boat. You're spot on, wrybosome, about the convenience of the parking lot, gear storage, shop/boat proximity and a fair sandwich shop within 100' of the boat for the lunch-munch between AM/PM dives.
I also like the dive site schedule; you have a pretty good idea of where you will be going, or, if you're the first to sign up for that trip, you get to pick your poison. As far as them not providing an in-water DM, there is only one op in the area that I'm aware of, Rainbow Reef, that offers that option at no charge. My druthers is one diver in the water is perfect (me). YMMV.
