Well, I just did a review of Embury and since that's always followed up by going upstairs to Firehouse Lounge, I figured I should do the same for that.
Firehouse is one of the most consistent club/lounges in Pittsburgh. The decor is funky but classic. The bartenders are pretty good and you'll find the wait staff pretty attentive, quickly flitting in and out of the crowd.
The inside lounge plays hip-hop on Fridays and Saturdays. The outdoor patio (covered in the winter) plays dancehall on Fridays and techno/electronic-shizzle on Saturday. Friday crowds tend to be sparser and there's more room to maneuver (personally, my more favorite day to go). Saturdays brings out the trendy, European-ish crowd. Either way it's usually a good time.