I'm in the same boat - we just got off the Fantasy 2 weeks ago and I didn't really enjoy it at all, but my family LOVED it so we've booked a BTB in January. I'm hoping to have a much better time this time and I'm going to force myself to enjoy it!
For us, the worst time was probably Costa Maya. DH "heard" me tell him that we didn't need to bring money ashore and only brought about $40 cash (I still maintain that I never said anything like that). Fast forward to an hour later when we'd spent all but $11 on a shuttle to the beach and entrance to a beach club. The guy who sold us the tickets SWORE that the shuttle would drop us off right at the club but it dropped us off a full 2 miles away, so we had to walk there (with our 3 small kids) in 100 degree heat. Once we got there we found out that they don't take credit cards (cash only) so we couldn't buy any food or drinks; we didn't even have water because I'd asked him to pack water and he packed ONE tiny bottle for five people. I ended up sitting on the beach crying while the kids played in the water a bit and endless people came by and tried to sell me stuff, DH walked around and tried to find somewhere where we could buy water with a credit card but couldn't find anywhere. We had just enough money to take a cab back to the ship (it was $10, so we had $1 left over) and when we got back to that little area by the port with the shops we tried to buy some water and their credit card machines weren't working! What a terrible day! We laugh about it now, but on our January cruises I've insisted that we book only
DCL beach days and I made sure I packed the excursion bags for the rest of the cruise.