First, read my thread talking about defection from RC. In the highly competitive cruise game, if I can go on a comparable line for less, that's where I'm going (as long as it isn't Carnival). When I say comparable, I look at Princess, RC and NCL about even.
I saw a 7-day Mexican Riv cruise that was more expensive on RC than an 8-day on NCL. I could care less about cruising on the "biggest, baddest, boldest" blah blah blah ship, which IS something that you are paying for - the joy of sailing on one of those beasts. Their ships are getting a little too big for me anyway. They're so big, it doesn't even feel like you're on a cruiseship, and that is part of the fun!
Bowmom35 mentions "younger" families. I can say that I've run into the same ages on all three lines I've been on, so it balances out. Kids are kids, from our experience. I would recommend that Beth tries another line, just to make a comparison (again, stay away from Carnival)
As for perks, what perks really? Another luggage tag? A nice toiletries bag? To me, no perk is worth $200-$300. After one cruise, you start getting perks from any of the lines, so what is the difference?
We're trying Princess for the first time in November and, depending on the experience, may be changing allegiance permanently.