A group of 6 of us just got back from Cozumel last week and we dove with BlueXTsea and could not have been happier. Christi went above and beyond to help us out (even taking me to the airport to pickup my son that arrived a day later, to save the taxi fare and make it even more convenient for me)
I concur with what has been said about her op previously, fresh water shower, fresh towels for each diver, homemade chocolate chip muffins, cold water and lemonade, SI at a beach club with great food (one day she made turkey sandwiches for us all), great DM's (pointing out all sorts of stuff) and captains (right there when you surface), thorough dive briefings and all of the 6 in our group dove our computers. A couple in the group are air hogs, so Christi provided 100's for them the next day without us asking so that we could all stay down as long as possible together.
All 6 of us earned our nitrox certification with her, she is also a clear and concise teacher. 2 of us went on and got the AOW certification through her too.
We came to appreciate her boat Shamu too, we were on 3 different boats the week we were there and Shamu was the nicest and fastest with a 215hp Yamaha outboard. The others were much slower. We were on other boats since BlueXTsea was one of the busiest dive ops last week, and Christi had to juggle a bit with the boats. Every day we were picked up right on time at a downtown pier just steps from our hotel (Casa Mexicana), but one day due to weather she paid for a taxi to take us to the Caleta. We motored out of the Caleta that day probably being 1 of only a dozen or so other dive boats out. Looked to me that other ops had no customers, but Christi had multiple boats going out, I think that says alot.
I am sure there are a relative few other ops on the island that offer this type of service, but this one I can vouch for firsthand.