Things to mention:

*: condor_hold actually kills the DAGMan process; condor_release starts a new process (but the same Condor ID)
*: lock file (including Joe's Unique PID thing)
*: re-reading node job userlogs
*: FD problems on wide DAGs
*: a bunch of places where we do special stuff in recovery mode
*: recovery mode is totally separate from a rescue DAG; in fact, you can be in recovery mode while running a rescue DAG.