I've come to the Nitty Gritty more times than I'd like to admit. I've eaten here upwards of 5 times, and not one of those times have been remarkable in any way, shape, or form. At best, the food is just okay.
It's always teeming with loud partygoers, even in the restaurant. This is too much for me when I'm just trying to eat food. Thus, I wouldn't recommend it if you just want to eat food and are not celebrating yours, or someone else's birthday.
The very worst part is that you have to hear the "Happy Birthday" song (not the one you're thinking of--a hellish variant) about 18 times while you're there.
The good parts? Excellent (and I do mean excellent) drink specials most nights. Prompt bar service. Free mug with the year on it for your birthday (with all the beer or soda you can handle). Pictures of past partygoers on the wall to snicker at.