I had a similair product for my Subaru a couple years back. It did make a huge difference in the throttle response. The drive-by-wire system on the car was laggy and with the module you would choose a level which would cut down on the lag. Pretty much makes the ecu think that you're hammering the peddle when in actuality its the module adjusting the throttle map.
As for the warranty, its a totally reversible modification. Just unplug it whenever you take your car in to a dealership for service.