Not on the Splendour, but we went on the Carnival Triumph. It was great. Food was really nice (both buffet and restaurant), plenty of choice, there was even a pizzeria and burger place, coffee shop with gorgeous cakes you could buy for a couple of dollars (huge slice of chocolate cake about 6 inches high etc). Entertainment was also good - there were show each night in the showroom, quizzes etc. Definitely different from Thomson's who we cruised with before, but still very much fun focussed and not stuffy at all!
You can take a bottle of wine per adult on board with you, cabin steward will help you chill it in ice. You can buy drink coupons for about $5.25 each in advance, which save you a little money towards the cost of your drinks. We didn't really spend a great deal on board though anyway. Captain's night was good too - they set up pre dinner drinks in the lounges before the dinner (they put a note under your door letting you know which lounge you were assigned to), and there were nice cocktails and wines handed out.
There was also a caribbean style band playing at the pool which was nice.