re: SQL2012SP1CU2 & stuck transaction log KB: http://support.microsoft.com/kb/2509302
I considered that, but
#1) That KB says it is for databases in Full Recovery Model
#2) It says it occurs as a result of a script run during upgrade. My stuck databases were all created on SQL2012.
This issue occurs because the "tran_sp_MScreate_peer_tables" transaction was left open by a replication upgrade script during the upgrade. This open transaction prevents usual log truncation.
#3) Following along the diagnostic steps given further down in the article
I don't even have this registry key: HKLM\SOFTWARE\Microsoft\MSSQLServer\Replication
and I get nothing back from
select * from sys.dm_tran_active_transactions where name = 'tran_sp_MScreate_peer_tables'