With VNC, you can get around the port forwarding on the customer's side by running the "listening viewer" on your end. They just right click on the vnc server icon, "add new client", and then type in your hostname or ip address.

Or even better, use UltraVNC Single Click to compile a executable where they can connect you with a single click.

That said, I use LogMeIn also . Works better because I can access it when I'm on a public or shared computer, or away from my regular hostname.