I took a cruise on Princess through the Eastern Caribbean over the holidays (also owned by Carnival, the 800 lb. gorilla of the industry).
General impressions:
Food was pretty good at the sit-down dining rooms, but not especially adventurous. Think the fine dining restaurant at a reasonably nice hotel in, say, Wichita or Syracuse. Not adventurous, but nicely presented, and harder-to-time items like seafood were well prepared, not oovercooked. (Not sure how they do it for 2,000 people x 3 meals/day + 1,000 crew members.) Definitely not banquet/rubber chicken stuff. Wine prices weren't bad, with a number of decent bottles in the $20+ - $30+ range. Waitstaff was uneven, but generally good - better if you sit at the same table and get to know the servers.
The surcharge restaurants were good. The Italian restaurant ($25 pp extra) had a nice Northern Italian 8 - 12 course tasting menu. Not overly conservative; it included a pulpo course.
The grills, pizzerias etc. were similar to what you'd get at a marginally competent independent hot dog/hamburger stand or pizzeria.
Buffets were better than similar operations I've had at all-inclusives on land, and reasonable only if you need an extra food fix at 3:30 am. Otherwise rely on the sit down dining rooms for your 3 a day.
Princess' materials will tell you you're limited to bringing aboard one bottle of wine, booze etc. They don't tell you that they only check your carryon luggage, not your checked stuff. We "smuggled" aboard 5 other bottles of wine in suitcases.
There's a $15 corkage fee if you bring your own wine to a restaurant - not bad if you want to bring something good. Obviously, no corkage fee if you have a cocktail party in your stateroom before or after dinner.
If you shop the duty-free liquor stores at a port of call, your carryon wll be inspected as you re-board the ship. They'll confiscate any hard liquor (you get it back at the end of the trip) but you can take a bottle of wine or a six-pack of beer per person back to your stateroom from each stop. If they're busy as you re-board, and you're feeling surreptitious, you may be able to "happen" to miss the liquor inspection table (at your own risk, of course ... but it happened ... my brother, afterwards: "but nobody told me to go over to that table ...")
Entertainment, lectures and demonstrations were uneven; mostly worth skipping.
Of course, all this applies only to the Princess cruise I was on; YMMV.