I've been to several of MB's On-Track events over the years, most recently at Pocono in 2006. On-Track is basically the same as the Challenge, but it's reserved for MBUSA, and MB dealership employees. To put it mildly, it's a
%#$*ing blast!!! Imagine pulling out of the pits and going full throttle all the way around turns one and two (passing is allowed on the right). Then, get on the brakes with both feet as hard as you can, hang a hard left, and tear through the road course section (no passing is allowed on this part of the track). Re-enter the main track at the exit of pit road and do it all over again. Of course, this follows some instruction from professional drivers. I ran about twenty five laps in a C55, E55, and an SL55.

Then there's the precision driving competition. SLK's were the weapon of choice for this timed event. This was almost as much fun as the high-banks.

My advice, spend the money, it's worth it.