I travelled to the Bahia Principe in Feb 2012. The accommodation was great (if perhaps not quite 5* standards) and the staff were wonderful. I've never stayed in a friendlier hotel. However, I'm not overly used to all-inclusive and I found it a little too far away from everything. It didn't feel very Mexican and to visit the 'real' Mexico, it became pricey and involved long coach trips.
The food was great and the beaches were lovely, although there were not many great places to swim. The entertainment shows are different every day but are repeated every week so once we'd been there for the first week we had little to do at night. The bars are great and cocktails yummy but at 24 we seemed to be the youngest people there. It wasn't perhaps the best place to go for two twenty-something girls.
Therefore, to round up...If you're not a fan of sight-seeing and you are looking for a romantic getaway for a few weeks, this hotel is great. If you're not looking for places to go out drinking and prefer nice meals and quiet evenings on the balcony then this resort will suffice.
I did have a great holiday but perhaps next time I go away I will rent a villa and do self-catering so I can explore a bit more of the country I'm visiting.