The atmosphere is quite variable, and I would very much say that it's what you make of it. Noise (once you're past freshers week, and it does decline throughout the year) has never been excessive (I've always been able to work / sleep through it), but you still get people holding flat parties etc. Anyway, I've always found it to be quite friendly.
A map will be your friend when interpreting this, but here goes: There's a large Sainsbury's and a small Tesco / Post Office about three minutes walk away, along with various fast food joints, bars and assorted shops (including everything from a brothel to the legendary Kebab King to an abortion clinic!!). All the shopping is centred around the crossroads between Wilmslow / Moseley / Wilbraham Roads, and then extending up Wilmslow Road, opposite Owens Park & Oak House (a map is your friend here). If you want South Asian / Middle Eastern food, then there lots of shops for that on the Curry Mile (Wilmslow Road, between Dickenson Road and the Hospital or thereabouts). For other things, e.g. clothes shopping, Chinatown, you'll need to go into the city centre. It's about 3 miles, and there are direct buses from outside Owens Park / Oak House, about every three minutes, which will take you straight there.
I'd say it's pretty easy to live here - everything you need for day-to-day living is on your doorstep, and there are benefits to having the large shops half an hour away - it stops you spending so much money! I've not experienced any problems that are specific to OH - everywhere has grubby kitchens and slightly obnoxious flatmates! I've never heard of any crime like burglary or assault being committed on campus - there are fences around it and security patrols which keep local ne'er-do-wells out. Despite being near some dodgier areas, it's actually pretty safe in Fallowfield.