I've used 25 mac's on an ubuntu server using netatalk and NFS. It's a disaster :
first of all, don't use home directories on the server with NFS. It is possible, but some applications (Adobe InDesign, Illustrator, Apple Mail etc.) don't like this. Apple Mail will in time complete mess up its mail database on the workstation, forcing to recreate all the mail accounts on workstations. Moreover, you will experience random freezes on workstations when the server is not available.
netatalk/afp (still) has issues with file locking. Adobe Flash (MX and others) don't like this, they'll crash randomly. Office for Mac doesn't like this either. Will hang randomly.
Using samba server-side is pretty stable with (Snow) Leopard clients. Older clients will experience random hickups, including (severe) permission problems. You can't use server hosted homedir's though with samba. You should definitely not forget to use
unix extensions = no
in smb.conf to solve some issues with file permissions.
I have no issues with running netatalk/afp alongside samba on the same server, other than that .DS_Store ._* and .Trashes files will show up in samba shares (you can easily filter them out on the clients, though).