Its great. Theres a bunch of clubs for different tastes in music, and theres always student nights that are cheap! Its big enough to have lots going on, but not so big that you can get lost in it. I love it, i'm looking forward to going back in Septemeber (i'm on erasmus)
It's alright. Quite a few clubs (Mosh is quite good), 2 shopping centres, plus loads of shops in the city centre. At weekends there always seems to be something going on in the centre too. Everything is quite close by too.
Personally, I think its pretty average- but then I am from London so I may have slightly different expectations from a city/nightlife to others coming from smaller towns/cities.
It's not loud, but it's not quiet. The city centre has enough shops to keep you satisfied, although it does feel a little artificial sometimes.
It's worth mentioning that students make the most of wherever they are. You could send a bunch of undergraduates to the North Pole and they'd still manage to have loads of fun there.