Sorry if you already know this, but just in case you don't (or for others out there):
There are 2 transmission modes with the shifter in 'S'.
If you just shift into 'S', you are in Sport mode, it still does all the shifting, but somewhat more aggressively, down shifting more readily, and holding longer on the up shift.
Once you press the gear select toggle, you enter SelectShift mode and your current gear is displayed on your cluster display. In this mode, it will hold your gear 'as long as feasible'. It won't let you over rev, and it won't let you stall, otherwise it doesn't do any other shifting. Now I would say that it's high end limit is still a bit low, considering how high the power band is, but otherwise it works quite well.
This is one of the things that they re-wrote in the updated users manual. The first printing didn't explain it at all, and had a decent amount of incorrect information.