I have it done. The gain is not as noticeable as some people on the MB forums claim, although my butt dyno tells me that it is indeed there (whether I should call it HP gain or HP restored, I'm not sure). As for issues with the electrical system, I had none, but my alternator did give out after about 10,000 miles of driving with the pulleys... my odometer only read around 30,000 km (20,000 miles or so). Coincidence? Not sure, but I haven't had any issues once I got new alternators for my car.