Most people notice a small increase in pep so to speak but no real HP increase. A chip is mostly good for removal of say a speed limiter, rev limit
minor adjustment for fueling spark advance, removal of EGR etc.
They are recommended for Auto cars as they adjust the shift points and make the car much more enjoyable. Not a bad increase over all and for the price can't be beat.
I really like my Diablo chip. It's not some huge boost like a turbo but it changed how the car felt. The way it changes your power curves around a bit makes it feel much more like a sports car and less like a souped up comuter car. The chip also removes the tip in. That alone is worth the cost of the chip to me. Much better throttle response.