Here is MSmooth 2.0 beta 1 for Avisynth 2.5. It is a detail-constrained spatial smoother as described in the original discussion thread:
http://forum.doom9.org/showthread.php?s=&threadid=31679
Of course it is not yet optimized for speed as I am just now resurrecting its development. It does however support both RGB32 and YV12. Please see the help file for usage details and the original thread for discussion.