On a related note, we took our first cruise as well last year.
We chose Princess (booked directly, although I have no experience booking cruises through TAs so don't read anything into that - all I can tell you is we got exactly what we wanted, although we wondered if we paid a bit of a premium for that. I also got some free "advice" from a former TA, who's been on countless cruises).
My point is we had an amazing time. We were on the Crown Princesss, which is newer (refurbished maybe) and huge. Really huge. And it was pretty full. Even so, we hardly waited in line for anything. We got great service, and loved all the amenties onboard.
This was a Caribbean cruise, from PR to Aruba and back. We are well travelled in the Caribbean, so we had little interest in getting off in port - except for a couple islands we had yet to visit, and even then just for an hour or so. So we spent a lot of time on the ship and loved every moment of it. We spent Christmas Day in "The Sanctuary".
One last thing - we found it was well worth the extra $20 or so to eat at the speciality restaurants. There were two, one a beef house, another Italian, and we loved both.
So we hope you enjoy your first cruise on Princess. We were so happy we would be hard pressed not to try Princess on our next cruise, and probably the Crown again.
Cheers,