okay, I'm not a mechanic but as far as I can tell, performance chips cant be all bad.. can they?

Does anyone have any experience or recommendations on them? If gas milage can be improved and you can get more horsepower as well as longer engine life then $70 is a good investment..

However, I could be talking out of my ***** too, but that's about all I can find on them...

so, has anyone done it? pros/cons/warnings/success/??

like i said, I'm not a mechanic, but there seem to be a large selection of chipsets..

any input appreciated