If you are looking for something that responds as fast as RDP for Windows does you may want to look into Nomachines NX product.  Very responsive.  However if you want to attach to the console it is only marginally faster than VNC.

Download the Client, Node and Server packages from http://www.nomachine.com/select-package.php?os=linux&id=1

Then simply run:

sudo dpkg -i nxclient.<version>

sudo dpkg -i nxnode.<version>

sudo dpkg -i nxserver.<version>

You will also need to make sure that SSH is installed and running on the machine:

sudo apt-get install ssh

Then download and install the client on a remote machine (windows, linux whatever) and point the client to your server's IP on port 22.  It should connect and startup a new X desktop for you.  Keep in mind this is a NEW desktop.  If you want to see the existing (console) desktop then you will need to change the  "Desktop" config to "Shadow" however as I mention this is only marginally faster than VNC.  Nomachine has been working on that feature to improve it.