*lives in Nottingham*
The Pitcher and Piano is a really nice place to start, it doesn't have any kind of dance floor and the drinks aren't particularly cheap but they do some really nice cocktials, and some of there expensive ones are really posh (There latest range comes in upturned metal tophats with sparklers etc, looks much better in reality than it sounds).
Once your done there make your way across the road (literally just over the road) to brass monkeys, it's a small cocktail bar that normally has massive queues at the downstairs bar, because nobody seems to realize theirs an upstairs where you can be served instantly. The drinks are reasonable and they have some really nice cocktails.
Once your done there I would personally take a bit of a trek to Vodka Revs, Nottingham has two, which most people in the area know as New Revs or Old Revs. Old revs is in Hockley, New Revs is at the corner house. Personally I think New Revs is better but there both pretty much the same thing. New revs has a decent sized dance floor that starts filling up later in the night.
If you fancy somewhere thats more of a dive with really sticky floors, Cucamaras is awesome. There leg wobbler will get you absolutely bladdered but the place really is a dive these days.
After your done in your warmup bars / shot places you have two main choices, either Gatecrasher or Oceana. Personally I don't like either of them, Gatecrasher just seems to be endless flights of stairs and getting to Oceana is like a mini hiking trip. A good place I like is Dogma. It's only a small club, and it's main dancefloor is in the basement (it's a decent size, probably about the same as one dancefloor at somewhere like Oceana) but it plays a good mix of music, normally with plenty of RandB. It's free entry all night, and the drinks are closer to bar prices than full on club prices.
In terms of the reputation for being shot, it's a load of rubbish. Unless your taking a taxi into the rough area of town and looking for trouble the center is no worse than any other big town.