Somewhere between 3 and 4 stars.
I have been there a few times, but I have postponed writing a review of Avenue B. I wish I could like it a tiny bit more to give a four stars, but it falls short of it.
On the plus side, the room is very enjoyable. Small, but not crowded, with ample room between tables. Nice acoustic. Big black boards.
The staff is helpful. And it's BYOB. And the food tends to be good.
So, where's the catch? *tends* to be good... It's a bit unreliable, and it's rarely fantastic. For the price, and despite the BYOB option, I prefer the other high scale in Pittsburgh.
My first time at Avenue B, a couple of years ago, the good was way too salty. This did not happen again, but some dishes I have tried have left me disappointed, although I have enjoyed others more. (Sorry not to give examples, I have no eaten there since early Fall.)
I will probably back at some point, but that's not one of my go-to destinations in Pittsburgh.