Just a final follow-up here for the benefit of the next person to use the power search button on t-m-o.

"Halloooo? Anybody?"
<sound of crickets>

My first attempts at getting the N900 to sync with my old 9300 met with failure -- that 9300 is at an old software release (6.03) and I saw repeated application failures on the 9300 whenever I tried to initiate a sync from the N900.

But on a hunch, I initiated the sync from the 9300 side (Tools->Data transfer). That went pretty well, and calendar/contacts migrated over bluetooth within about five minutes or so.