Thanks all - I've already had a few typical hellish commutes, smashing over nasty surfaces while squeezing between buses, etc. The repair is holding up just fine so far, happy to say. Bike feel tight, so I am guessing they did a little alignment which may have straightened the 30-yr-old frame's tracking?

I'm also happy to report I have been trolling CL for weeks and finally scored - found another Trek 500, in great shape, at a decent price (an '85, the year before this, so no "tri-series", and it's Reynolds 501 vs. the 1986's 531), and although they are advertised as the same frame size (both top tubes are 53cm), the new-to-me 1985 is slightly bigger overall and feels great! My repaired 86 was a wee bit on the small size vertically, though fine for commuting, as a little extra standover never hurts in the urban jungle. Though it's a slightly larger frame, the 501 bike feels heavier, but a lot stiffer! I kinda prefer it so far...

In any case, am quite stoked to have my old commuter back, plus a new backup. Very nice riding bikes. Thanks again to all for their help, and well-wishes.