I was on the Paradise in December and loved it! My partner wasn't able to go, so I went with my dad (who is also gay) and sister. (who's not). It was the first cruise for dad and myself and the second for my sis. Post-cruise, we all agreed that it was the best vacation any of us had been on.
As luck would have it, there was a gay couple seated with us at dinner. They were in their 40's, from NY (with thick NY accents) and an absolute riot. We also noticed several other probable gay and lesbian couples, but didn't really socialize with them.
The ship is incredible, much nicer than I had expected. The smoke-free aspect is a huge bonus.
When you get to the port of Miami, the Paradise looks very small compared to the Victory, RCCL Voyager and NCL Norway that are all also in port. Don't let that fool you though, once you board, you'll be amazed at how large and beautiful she is.
As for the Carnival line itself. You'll read lots of reviews that poo poo Carnival in favor of Princess and Celebrity. I'm going on my first Princess cruise later this month and have never been on Celebrity, so I can't yet compare the three. I will say, however, that your cruise will be what you make of it. If you are expecting a 5-Star experience (for a 3-Star price), then you will likely be disappointed. If you keep an open mind and focus on the positive, you'll love it as we did.