Windows file sharing coupled with smbfs mounting is slow. Very slow. On a 100Mbit switched link I was getting performance of about 2.2MB/sec actually transferring files.
I started getting angry, so I decided to grab cygwin1.dll and rsync.exe from somewhere, fire it up in daemon mode and retry the transfer. Now I'm fetching files at a rate of about 8MB/sec.
Yay.