FWIW, this must be the thread I was thinking of in my initial post here:
zerothread?id=229339
(thanks for the help with searching the archives, beancooker!)
Just to followup, but my dealer didn't notice any problems with my car when they tested it last weekend (figures). It happens pretty consistantly for me though. It's almost exactly like the documented problem with the 2003 and earlier G35 transmission's though. A harsh transmission shift at low speeds, and slow ability to engage at all speeds. Frustrating.