I can add a bit for sallies (though i'll probably forget a lot so please add more!)
Location: Practically in the centre of town, closest hall to a lot of the arts buildings. Not quite so good if you're doing sciences, but it's a short walk home if you've been out at night. We back on to the scores, and some of the rooms have amazing sea views. Downsides, can be a bit chilly! Right next door to Younger hall (the music centre etc...), and about a minute from the library.
Accommodation: OK, so I'm biased but sallies is one of the 'prettier' halls (ie. one of the older ones). Within the main building, there are three floors of rooms (A,B and C floor) with a couple of rooms on the ground floor. There's also D block, which I don't know very much about apart from they seem to put returning students there.
If you're a first year, chances are you're going to have to share a room at sallies. Room sizes do vary, from slightly snug to very spacious. As a warning, some of the internet connection points are in really strange places (behind a bed on the opposite side of the room from the desk) so a reaally long cable might be required. Bins get emptied and sinks cleaned in the rooms, and the bathrooms get cleaned every day (not at weekends). Rooms get hoovered once a week.
Other facilities at sallies include the basement (laundry room, table tennis and huge snooker? table), big common room (reasonably comfortable chairs, free papers, drinks machine, tv and grand piano), study room (v. quiet), small library and computor room (handy for 3am printing!).
Bathrooms are, suprisingly, almost always quiet. there's one toilet between about 2 and one shower between about 3 on our end of the corridoor. There's even a bath tub lurking around somewhere!
Food: Sallies is fully catered (19 meals a week), but we don't get dinner on saturday or sunday. The food does vary (big emphasis on potatoes), but there's always a veggie option and some sort of salad available. I can't really comment on breakfast, apart from it's too early!
There are 2 (I think) kitchens on each floor for midnight snacks and cooking at the weekends. They are small, but have a fridge, microwave, toaster,cooker, hot water urn etc. However I wouldn't advise leaving pots and pans in there as they may walk.
Atmosphere: First of all, we're not as posh as our reputation! It's really easy to find friends here, especially during meals. Apart from that, coffee and cake on a sunday afternoon with the warden is not to be missed!