So I upgraded to the new version and decided to try out the new, improved Dropbox sync.
It failed at first, and I could see that it was trying to sync to /Trunk/notes, where /Trunk was the directory I had previously entered in the settings. Seeing there was no notes subfolder, I added one and synced again. This time it went all the way through, but I probably should have realized that syncing to an empty folder would wipe out all my notes, except a few, for some reason. Perhaps a warning dialog would be in order, something like, "This sync operation will result in the deletion of n notes. Proceed?"
Once all these notes were deleted, there seems to be no way to recreate my HomePage. If I tap the home icon, it brings up an empty HomePage in the edit view, but does not allow me to save it, with or without contents. So, I deleted the app and reinstalled it, restoring from my last email backup.