I'm very happy to report that gnome has evolved from a hair-tearing
nightmare to a joy in just one week's time  :-)

Thanks to everyone for the fixes.  What an improvement!

One caveat:  I just did a fresh install of gnome on a -CURRENT
machine, so no package-upgrades were involved.  Maybe this is
why things worked so much better today than last week.

Anyway, a fresh install works great and can be recommended if
someone can't get an upgrade to work right on -CURRENT.