Have these "new" UPnP issues mostly been resolved in 2.5.5.0? Others added?
More specifically, would the current 2.5.5.0 still be considered a regression from 2.5.3.0 or an improvement overall?
As there are still 2 open
trac tickets,
152 for 2.5.4.0, and
160 for 2.5.5.0 (2.5.4.0 working).
There have basically been 2 relevant updates to UPnP.
r8772+
r8775+
r8778 in Sept.2010 for 2.5.4.0, and
r8918+fixes in late Feb.2011 for 2.5.5.0, presumably in regards to this thread.
One specific issue mentioned seems to be multiple network adapters.
The other random port registration bug would probably be related to the ongoing random port bug in 2.5.5.0, which has been identified but not yet corrected.