Thanks for all the responses - really interesting reading. I'll try to respond to some of the main points,
I will be the first to admit, some of my "requirements" have no technical basis, but I'm OK with it, e.g., I had a bad experience with aluminum a long time ago. I will be the first to acknowledge that manufacturers have most-likely tweaked their designs such that it no longer feels like I'm riding a jackhammer, and if aluminum was the only frame material that checked all the other boxes, perhaps I'd consider it further. However, I know both Ti and SS do check all the boxes (and allow my anti-aluminum prejudice to continue unchecked), especially for a bike that I plan on keeping for 20+ years. As far as carbon goes, I'm not convinced that it's the best choice for a bike that will be used for 20+ years (besides, Calfee never returned my email inquiry - a sample of one, I know, but it just adds fuel to the fire). One of the main attractions of both Ti and SS is the ability to forego paint and not worry about scratches (until I'm ready to deal with them). Cro-Moly steel with a powder coat finish would be another alternative (although the local custom framebuilder insists on using wet paint - looks great, for a while . . .).
As far as cost goes, I'm aware this exercise will not be inexpensive, regardless of material. This likely will be the last bike I buy (well, there may be one more . . .
). I do have relatively secure parking at work (enclosed bike lockers in a parking lot that is patrolled by security guards); besides, that's what insurance is for. There is the concern about running errands after work, but in the past two years, I've only done that once or twice.
I also am a bit concerned about the ride characteristics of Ti, but I figured one of the advantages of working with companies like Seven or Moots, is that I'm most likely to be able to have the ride tuned to my needs. Same goes with SS, in which case the local custom frame builder would get the nod. My (custom steel) road bike rides like a dream. I'd happily commute on it (and I have), but I do worry a bit about scratches as I put it into the bike locker, and while it does have fender mounts, it doesn't have rack mounts, so I see it more as my Sunday, fair weather bike (maybe a few years down the road this will change); this commuter will be the foul weather, commuter, maybe even a little off-road. It may get wiped down after a rainy commute, but likely it won't, especially on the ride in to work (that's why corrosion resistance also is high on the wish list).