Among the casinos, Borgata is (IMO) the nicest, and in the fall has some good mid-week specials. Only drawback is that it's in the Marina and you can't walk to the other casinos from it, but its casino has the best (most "Vegas-y") vibe, in my opinion.
I've also stayed at the Tropicana, the rooms are fine, if a bit small, and they have good midweek specials too.
If you want someplace with a "party" vibe, but not a casino hotel, the Chelsea is supposed to be the "happening" place. On weekends, it can be expensive, but I'm told it has some surprisingly good midweek specials.