I don't recommend Big Bang to anyone looking for a great place to socialize - but if you have a few friends or a group and want a rowdy place to have a couple of drinks and sing along to pretty much everything you've ever heard on the radio, go for it. It CAN be a blast if you go with the right people. The music is usually great, and 70% of the times I've been at Big Bang I've had a great night.
But it is not for the faint of heart or the discriminating drinker. Drinks are overpriced and generally average in quality - definitely nothing exceptional. The space is crowded at best, but usually packed from the window to the wall (yes, sweat will drip). At best it's not a place to go unless you feel like vyying for a table to sit at and being jostled, bumped, and shouted at.
But again, if you have friends that can hold their own in a rowdy party environment, it can be a complete blast.