We have used Services for UNIX for years. Mostly for the NFS portion which allows our SGI
workstations to jive well with their MS counterparts. SAMBA and similar tools just don't compile well on some versions of HP-UX and AIX so Services for UNIX has saved out hind parts many times. The password management components are also a large benefit. FYI, Trying to get things talking to an AD setup seems to create as many or more problems than it's solving with the 3.x versions. The initial configuration was painful for us so we gave up.

Of the many 3rd party Win<--->UNIX packages, this one is worth trying if you have the need.