smb is fast on windows, smb2 even faster. its your osx client that sucks. i remember trying to use smb over wifi on osx 10.5 - failed 99% of the time on large files. the same setup (wifi laptop, same range was 10% failure on same files). hell osx smb fails on ethernet still randomly usually long file moves (10-60 minute files).
here's the kicker - fire up fusion/parallels and the SMB on the apple went from 99% failure to 10% failure (!!) in the vm. problem solved.
osx smb just blows. kinda like osx RDP client (its faster to use a VM and windows RDP)