The menu changes daily. It's actually posted up on the website somewhere, so if it were term time you'd be able to spy on what they were serving. I remember being very impressed with the quality when I first arrived, but the appeal declines in time. Not sure whether that's because they try harder at the beginning of the year or if you just get a bit tired of it.
Since you'll be either in Cripps or Dokett I'll talk about their kitchen facilities. In Cripps you share a kitchen between 6-8 people, and it has four electric hobs and two fridges. You might be lucky and find a microwave that a previous occupant has left, or else you could each put a fiver in and buy one for your kitchen. There's plenty of storage space in the kitchen, I think in Cripps you get a lockable cupboard per person. Anything you can't fit in there you can keep in your room.
Dokett you get a kitchen between four normally, unless you're on a Peculiar floor and have to share the kitchen below (it's the joy of Dokett that there -are- peculiar floors, much better than the modern buildings which are so uniform). There are two hobs and a fridge in that, and normally a couple of big old wooden cupboards which aren't lockable. So possibly a little less cupboard space, though with only four of you there it's easier to just leave stuff around.
If you know what day to visit which restaurant then you can get plenty of student discounts. Tuesday night = 2 for 1 pizza at The Cow, Wednesday (I think) = half price at Bella Italia, apparently the tapas bar near John's has all you can eat for £10 for a few days a week. I don't remember there being a standard discount anywhere, so it can end up pretty expensive eating out.
Having said that, Dojo's should be discovered asap.