Been here a couple of times. It's a long wait but it's worth it. These guys have their cheesecake baking down to an efficient process and the quality is incredible every time.
Note that the line outside is only part of the wait: it continues inside. By the time everyone waits for 90 minutes, they end up ordering as much as they can which usually slows the speed at which it moves a little.
Don't eat your cheesecake right away! I know it's tempting, especially after such a long wait, but it's better if you let it set for an hour or two in room temperature. Also try refrigerating it overnight to give if a thicker consistency (but still fluffy and not nearly as dense as New York Cheesecake).