Put Amsoil 0W-20 synthetic in my tranny a couple weeks ago ( '07 roadster with 5K miles), and it seemed to make the shifts a little crisper with some cold weather improvement. However, the "notchiness" is still there.

Love my X-Fire, but man, it shifts like a truck or a FWD vehicle.

I recall road tests critiquing the smoothness of the original SLK 6 speeds back in the mid- 90's.

Guess the choices are to either live with it and shift carefully or get an automatic.