I've got three identical machines for my 3 kids, running Narwhal, but I'd like to replicate the user accounts across all 3 so anyone can login on any machine without me having to create all accounts on all 3 machines.
Ideally, this would include storing their home directory stuff on a windows server (or one of the 3 machines), and replicating their desktop settings, etc. The windows server is all set up, samba's running, I can map it, etc. I just haven't bothered yet because I didn't want to replicate the same work 9 times. (15 if you include the guest account and my account.)
If your Windows server is a Domain Controller, you can use Likewise-open to join to the Windows domain. See e.g. this: http://galigio.org/2011/06/13/including-a-ubuntu-machine-into-a-windows-domain/
You might want to look at setting up an OpenLDAP server if your windows server isn't already doing authentication for you. There is a nice guide here: https://help.ubuntu.com/community/OpenLDAPServer
It is far from simple though, so you might have better luck just centrally mounting the user home directories, or using rsync to keep them in sync.
There are also a number of terminal tools out there which will let you simultaneously execute commands on multiple ssh sessions, which might shave some time off for you. My favorite is Terminator, but I haven't used many of them.