After much angst, I am now happily syncing my music library and playlists between a Windows 7 PC, my Transformer, and my Android (Nexus S) phone.

I installed MediaMonkey on my PC. I think you need the premium (not free) version.

The initial configuration on the three devices is not exactly intuitive, but once set up it is stable and simple. When I open MediaMonkey on the PC and then plug in either android device, MediaMonkey recognizes it and syncs on command (or autosyncs if that option is selected). Either the generic Music app or PowerAMP work fine on the androids.

If anyone wants help, I will post the exact configurations that I am using.