They changed the M3 in 2008 to a 4.0 liter v8 from a twin turbo v6. It was making around 360 hp with the v6, but they upped it to 420 with the new v8. It really is an impressive engine, you should see the tests they put that car through. GoodysGotACuda also already mentioned the "buttons". There is different settings on an M car, daily driving, one other and M Mode, which is max performance. They are very quick, nice handling cars. I want one so bad, but I can't afford it and also I have a 6 wk old son so we need the 4 door car.
Nice kill though, that was definitely one of the better ones considering the performance of the M.