Upgrading from OS X client to server

[ericmurphy]

Is it possible to do an in-place upgrade from OS X client to OS X server, without having to recreate user accounts and reinstall applications?

I'm considering installing OS X Server on my main machine (a dual 2 GHz G5), but I might not do it if I have to reinstall all my applications and recreate all my user accounts.

My plan would be to do this post-Leopard, but I'm assuming if it can be done with Tiger, it can also be done with Leopard.