i went in April 2008 on a university trip and had a brilliant time, we spent hours and hours (literally all day) walking through the streets of Barca and it really is an amazing place.
i cant really help on places to stay because it was organised for me.
the nightlife is great tho if you find the right places. however it is very very expensive. we went to a club where it was great inside, but it was 12euros for just about every drink. i was on jack daniels, and to be fair you did get a long glass full of the stuff, but it was still very expensive. however, you can find cheap places, i have no idea of the name of the place we found (though i could find it on google earth), but it was a local bar where the beer (locally brewed estrella) was dirt cheap, the equivalent of a pound per bottle (compared to £5 per pint in central Barca). every few rounds they brought us free spanish omelette and nuts, free rounds of beer, and even saved us a front seats when Barcelona played FC Twente in the champions league, sitting with the locals it was a great atmosphere. a few days before we went to see em play getafe at the nou camp for about £35 bought on the day at the nou camp which was well worth seeing despite it being a 0-0 draw! they even allowed people to smoke banned substances in there with the bar staff!
we were told to watch out for pickpockets but had no problem but were always in groups of 3-5 (or sometimes 38). skanky hookers were everywhere at night, drug dealers were everywhere in the centre and on the beaches in the day (they will try to rip you off too).
i hope that side of things is cleared up a bit.
[ Edit: Edited on 24-Feb-2009, at 04:55 by si403 ]