Amsterdam is awesome. They serve up the best and the strongest martinis and play some pretty great tunes.
I'd say the clientele is mainly men, but there are plenty of girls mixed in. The bartenders are fast, which is important and the decor is upscale.
I haven't been to Burn yet, but before that club opened, I'd say Amsterdam was the nicest alternative bar we had. It still may be, but I've heard a ton about Burn and all my gay guy pals are flocking to that place like mad, so it may have overtaken Amsterdam. Either way, it's still a great place to go for a fun night out, whether you're gay, straight or in between!