While I semi-ranted on the need to get out of the french quarter below, I want to add, that for nightlife/drinking, you can get pretty much all you need within the quarter.
From daqueri's "to-go" to rooftop drinks, you cannot go wrong at night in the quarter. I am one of those that still loves Pat O'Briens, and can sit for hours, trashed, singing along to the dueling piano's, especially when someone comes out to play the plates. Napolean House is another classic that is really is classic. The scene in JFK where they sit in Napoleon House in the rain and watch TV, IS Napoleon House. You will get all the music you need in tourist stretch along Decatur and all the drinks you need at the various other bars. A couple more great choices include the old schoold saloon attached to Tujagues and the crumbling Lafite's way past where bourbon street is bourbon street.
Like the food, the bars outside of the quarter are a bit more New Orleans than the bars inside, but I do not know if the New Orleans bar, to the general tourist, has much to offer. The primary experience of a New Orleans bar does not truly come out until well past midnight. If for instance, you found yourself in F&M at 9 pm, you would really puzzle at all the fuss.
Then, again, nothing can beat late afternoon drinks at the Columns...