Yes, Sex on the first date is always OK. And I am here to help you, as a woman, realize this, and spread the world to all womankind, that you should definitely be having sex on the first date.
*smile*
Actually, everytime I tried to postpone sex to make the relationship last longer, it never worked.
With my wife... I met her in a bar, and we went home about 30 minutes after meeting and started hittin it. less than 2 years later we were married.
So, it isn't necessarily bad. just go with the feelings and don't reject it just cuz it's the first time.
To be honest, as a guy.... if i like a girl, I'll want to be with her, and whether sex happens on the first date or later, wouldn't change my opinion of her one bit. In fact, I would probably dig her more if she attacked me on that first date.
anywho... that's my 2 cents.
-j69