I had thought about getting a super chip tuner, but everything I read said that tuners work much better on diesels, and you don't get much improvement with gas engines.
From my experience you put the chip/programmer on for fun, you will NEVER recoup the cost in fuel savings, the power increase is noticeable but power equals fuel, so if you want it add it, but it's mostly just for fun especially at a stop lights next to some kid in his rice burner. VROOM VROOM!
Had tuners on gas and diesels, and while improvements of 100+HP on a turbo diesel was typical due to "SO much room to grow"
the SC 1865 gas tuner that's sitting in front of me gave about 20 hp and 30 lbft... certainly noticeable and as long as you didn't USE that increase all the time, like TT said, it won't pay for itself, but it will bounce the mpg up a bit...