Interesting accounts. . .
My fiance and I looked at Tiffany's early on in our search, and the salesman had to explain to us the "classic"-ness of the Tiffany six-prong. However, my girlfriend wasn't blown away by it, as a matter of fact, she felt that the band was too thin and would have preferred something thicker. (Although the salesman was a little stunned when we asked if Tiffany's had such a variation -- we didn't know how *classic* their setting was)
With that in mind, when time came to buy the setting, I went to a number of jewelry stores but eventually purchased my setting in San Francisco, CA at a store called Derco Jewelers. They have a huge variety of settings, most of which are variations on established styles, such as the Tiffany 6-prong, the Lucida, the Cathedral, etc. Keeping in mind my fiancee's preferences, I went for a modified Tiffany 6-prong, with a thicker band and a lower head, since neither her nor I wanted a stone that sat too high and caught on everything in sight.
Now that it is sitting on her hand, we both agree that the thicker band as well as the lower head have the exact appearance that we wanted (I'll have pictures soon, I promise!)
So in my experience, it seems like there are quite a few vendors out there who sell variations on the Tiffany 6-prong, from the head height, band thickness, and even how the head is connected to the band (some taper, some do not). Best bet is to check these out in person. While one can do a lot of research on stones (and read up in forums like these), I think it makes sense to hold and feel settings in person and put them on fingers to see how they fit in the context of a unique individual hand. I'm glad that we did.