The "Desktop Sharing" settings that come installed by default seem to use VNC. VNC is a bit of a bandwidth hog, can only work at the resolution of whatever screen is attached to the host, and mirrors every action on the host. (It also seems to work poorly with compositing, but maybe that's been fixed.)
I know about X tunnelling, but that's annoying to use and doesn't always work properly (or, more accurately, some apps don't work properly).
Is there any kind of protocol in between the two, similar to RDP used for Windows? Specifically, something that can run at a different resolution to the host screen and is a little lighter on the network? (Ideally, the more the protocol could have in common with RDP, the better.)