I've brought in more than my allowance of booze on numerous occasions and declared it everytime. I've never had to pay duty.

A month ago I brought in a bottle of JW Gold and Green from SA thru DFW without any problems; the guy I was traveling with brought two bottles of scotch and two bottles of wine and didn't declare them (he does this regularly and has never been caught). I never had a problem declaring it, so I always do.

Like the previous post said, if you buy it at the duty free you will have to put it in your checked bag after clearing customs.