We have an M5 in the family and I have some seat time in the M6 so I feel qualified to give you what you will end up hating about the M6..
The car drives and feels heavy. It is not a sports car. It is a Luxury car with a big motor.
Yes it is fast, but it does not turn heads like the NSX.
You will fight the car around because it does not drive like an NSX.
A huge Contention for me, the SMG transmission on these cars is terrible.
A few examples of issues...
Put the car in drive and you will experience the slowest transmission changes that you have ever felt. They make your whole body sway forward and back while it changes. Step on the gas a bit more and it only gets worse. Hard accel, throttle cut.... Pause... Shift.. Hard accel again. It drives you insaine, but it does not do it right away, At first you will think that it is something that you can live with, but it will send you to the funny farm after a couple of weeks! If you think you can over come it by changing to the paddle shifters you are wrong, they are slow too. The only time the SMG is on top of its game is if you are going 90% throttle or better and then the trans is really snappy! but with gas prices today, that will end up being an expensive habbit to try to addopt.
Second reason, You are pulling out into traffic from a stop at an intersection. you think you have an opening so you step on the gas pedal and then back on the brake fast because the opening dissapeared for a second and then you are back on the gas to get out into traffic. The clutch will sit there and studder or not engage quickly. This is a known problem with the transmission. So then because the car did not go anywhere when you wanted it to, you have to hit the brake again because the opening closed.
This same thing happens as you roll up to a right turn, the trans is in second gear. you pause, (but keep rolling) look left and then step on the gas pedal. The car just does not do anything as it hunts for the propper gear or the clutch is not "ready" to do what you want it to.
It has caused a couple of near accident situations in our family between myself, father, mother and brother driving the car. Our M5 is a lease car and we can't wait to get rid of the thing. It is one of the worst "sports" cars we have ever owned.
Also.. Why The F*&$ Do you have to have launch control to get going off the line fast? I mean really. It feels like you are typing in the cheat code to Contra trying to get it into Launch Mode. Yes it is cool, but not really effective if you are trying to play with others on the street.
If it had a regular manual 6 speed. the car would be much more fun!