I regularly shoot with a mixed set of super and standard speeds, as do many DPs. The 6 lens set of supers, 18, 25, 35, 50, 65, 85, is usually rounded out with a 100 & 135mm standard speed. It's also nice to have the 40mm standard as well.
I love shooting and mixing the sets too. I recently picked up a 40mm for my set and I love it. It seems to always be my starting point when looking at a scene. I'm looking at adding a 100 or the 135. Based on your experiences with them, which one would be the must have addition to the kit. My gut's telling me the 135, but I'd love to hear opinions based on real world performance.