I am a student studying cruise ships and as part of my programme I worked onboard QE2 for two contracts totaling nearly a year. Life onboard is not all that different to working in a hotel environment, so long as you remember that you will be with the people you work with 24/7 there is no escape, but saying that, it is a fantastic life - nothing compares to waking up each day in a different port or even at sea the views are amazing.
If you are joining the QE2 as an assistant waiter you will be assigned to a station in a restaurant, you would be expected to work breakfast lunch and dinner on sea days and on port days you may be given lunch off, it works on a rota system so that there is a fair chance for all. You may also be expected to work some shifts in the Lido the informal dining/buffet style restaurant. When you first join you may be with many others and in a programme called the White Star Academy - a bit like a training college at sea, they will teach you everything you need to know.
As for ship life there are plenty of facilities for crew, you will not have time to be bored there are lots of recreation facilities including a library, bar, gym etc. There are often crew entertainment nights in the crew bars and there are often crew excursions in exotic ports. You will be allowed time off in port (although not every port) to go out, shop, explore, eat etc.
Personally I had a fantastic time, so much so that I hope to return once I have finished my studies.
If you want to know anything else, drop me a mail or write a message on here and i'll try and reply. The QM2 runs a different system and I don't know too much about it, perhaps there is someone else out there who can tell you more about her crew.