This is one of my favorite bars in Pittsburgh. The bartenders are fantastic. Even when the bar is packed, they do a pretty good job at getting to customers as soon as they possibly can. Once the recognize you as a regular, you'll get even better service. Be prepared, though -- they make STRONG drinks.
I haven't had much of their food or heard much about it, so I can't comment there. I generally enjoy the atmosphere and strong drinks as mentioned above. I also like having the option to check out the DJ/band upstairs. I like that the cover isn't paid by everyone when coming in the front door, but instead, only people interested in the actual event can go upstairs and pay the cover charge.
It's been fairly hit or miss there lately as far as how crowded it is. Your best bet to get a table is to go earlier in the night (8-9 PM), though, in my experience.
One last thing... I saw that someone mentioned in an older review not being able to stand the smoke at Brillobox. It's all non-smoking now, so that's no longer an issue.