I drink lots of coffee too --mine is typically iced with fat free 1/2 and 1/2 and sometimes splenda. And, it's usually only half caffinated.
I'm with information on this one: I don't think coffee sabatoges the diet. The SBD book says that caffiene is an appetite stimulant. I don't find that to be true for me, though, so as long as I'm hydrated I don't worry about the coffee.