Benchmark got his installed several weeks ago and highly recommends the mod (I thought he posted the details but I couldn't find it). I'm getting it installed on my car this Monday.
It basically re-maps the throttle response and gets on the gas a lot quicker. Blipping the throttle for downshifts becomes easier (unresponsive in standard mode). No gain in horsepower. Not suitable for stop & go traffic.
This can be added to all 01/02 coupes/roadsters with the S54 engine.
Not sure why it didn't come from the factory already enabled. All it requires is a switch, wiring and a small circuit board to light up the Sport Mode light on the dash.