Not very familiar with the German speaking part of Switzerland and especially not Grindelwald but I am looking forward to doing some exploration this summer with better weather conditons and a great car!
In the mean time have a look at some pictures I posted of the region around where i live:
http://www.ferrariforum.net/forum/viewtopic.php?t=2130&highlight=
A couple of other FF members have also posted some stunning pics of Swiss landscapes with Fcars.
As for the speed limits, they are quite strict and very strictly enforced. One has to be very carefull and/or drive to Germany (a couple of hours away), tracks etc.