Personally, PE's have become my ski of choice over the past couple years (80mm waist), while they don't grip the ice like a race ski (or any decent ski with a 60-70ish waist) they have performed exceedingly well all around, and I consider them the best bang for the buck ski on the market. I just got new PE's (85mm waist) and will be trying them out this weekend, hopefully they'll still be as good as the originals. I also have Pistol's (95mm wasit), which I have to admit turn surprisingly well, and hold surprisingly well on the ice too (I'll be ordering the Vicious as soon as I can - yes, I like K2 skis). Now, on those icy New England days, I tend to break out my Fischers (Rx8's - 68mm in the waist I believe). I also have a fair assortment of other skis ranging from 65mm waist to 92mm waist, I just figured I'd K2's since they perform the best all mountain, IMHO.
Through my experiences, slower edge transfer is neglegable with the wider waists (if you're slow edge to edge, its you, not the ski), however, I have noticed some torsional issues with the wider skis and putting them up on edge, and I have felt the skis "fight" being on the edge, but this has only happened when exceeding 90mm waists (I have 2 pairs of skis that exceed 90mm waist).
All in all, I think it all comes down to personal preference and experimentation to determine what width waist is best for people. Being a primarily east coast skier (except maybe 1-2 weeks west per year) I find that 65ish - 85 is typically going to perform well on the east. The bigger sticks are fun though for those few "deeper" snow days and for bringing on trips.