Big Bang is a pretty sweet thing when you consider how many cool spots there are in the Valley. Residing under a bar where the women dress as slutty librarians which is under a Hooters, there are a lot of expectations for a place like this. Unfortunately, it really doesn't do much right.
The music is fine but there are a lot of places where you can't see the piano. It is just one of the limitations of the building. The place is spread out over about 5 different levels which can either be hazardous or entertaining, depending on if you are the drunk trying to navigate back to your seat. There is a bar at each end of the place but the lower/smaller one is the only one open during Happy Hour. If you want to avoid college kids wearing $200 jeans, this is not a place for you.
The positives are pretty awesome though. $3 everything except Red Bull during Happy Hour is a pretty wicked deal. It is close to the LRT stop on Mill Ave so it makes drunken bar hopping easy. The booze selection is pretty good and the entertainment gets better as the night goes on.
It's not a bad place. Shout House is a bit better but is way out in Glendale and doesn't have LRT access. If you want to go to a Piano Bar, this is a pretty good place.