I've been forwarding X over ssh for a while now and it totally rocks compared to VNC. It's secure and you don't need to have an extra service running on your machine.

If you are just using a server locally and don't need any access from the internet, I guess you could use VNC, but it wouldn't be that secure. To use the builtin vino server, you would need to set the machine to autologin and then set the server to use a password or whatnot.

If it doesn't have access to the internet, you should be "ok" but I'd not use VNC on a server I could just SSH into.

@HermanAB: I use XMing on Windows machines along with Putty to forward X over SSH. Works fine so far.