Good kill...with your 1/4 mile times you shouldn't have too many GTPs giving you a hard time.
As a recent convert to a Regal GS(supercharged), I can tell you that is is definately quicker than my 95 GT Automatic Convertible. I suspect my GT ran mid 15s and the Buick runs low 15s. They are however, very easy to drive fast. The automatic is pretty good, with a somewhat loose converter. I have beat stock 96-98 GTs, but as far as Mustangs, thats as far as I would go. Traction is a definate problem, even with the traction control.
In case your wondering, I had to sell the Stang since the car seats for my new twin boys would not fit in the back. I plan on getting a 92-93 Stang as a project car pretty soon though.
Take care,
Dave