Pros- You meet lots more people
Depending where you are it can be cheaper than living in a house
You only have to move a few feet down the corridor to talk to your friends.
Bills, internet etc are all taken care of for you
You pay at the start of the term when your loan comes through so you don't have your student loan languishing n your bank account for three months begging to be spent.
For girls, getting ready in someone's room as a group before a night out is awesome.
Cons- Shared kitchen. Your food will probably be stolen.
All those people that you meet make a lot of noise. Like me, you may be unlucky and live next to a girl who enjoys frequent loud sex.
If there's someone you don't like it's impossible to get away from them.
Exam period can be hideous if your neighbours are inconsiderate
There tends to be one kid who only enjoys music if it's at full volume. This may not be true of all halls but it was with mine. In fact, since I lived between loud sex girl and loud music boy it was acknowledged that I definitely had the worst neighbours in our halls.