I like my chip, and mine is a stick... Supposedly the automatics gain more from it, because it stiffens up the gear shifts. I haven't had my chip long enough to notice gas milage differences, but I do know you need a minimum of 91 octane fuel.
I'm assuming it will run like crap, but I don't know... I was told it requires 91 to 93. I know my 91 300zx runs terribly if you put the cheap gas in. I would assume it couldn't physically hurt anything considering the engine was made for cheap gas and only the chip has changed.