1) The upgrade evidently *deletes* directories pg_tblspc, pg_twophase, and pg_stat_tmp from the postgresql data directory. Google said to recreate the missing directories and indeed Postgresql then was able to start.
That's a good way to corrupt your data if using 2PC and tablespaces. (Be sure to take a backup before the upgrade).
2) SystemStarter is no longer available. Gulp… I am not a very good plist creator. Is there a fairly generic plist I can edit to specify my locations of the software bits so I can have postgresql started at boot time?
That's not surprising, this feature is deprecated in Mavericks. And launchd?