I recently discovered an excellent client application for connecting to X remotely. NX is a client/server application developed by NoMachinewith some clever caching techniques which provide near real-time response for X-sessions. The NX server works with an SSH server to provide secure authentication and SSL encrypted traffic, if desired. A GPL'd server has been written and is available here, while a free client is available from Nomachine.com. The NX client will also connect to Microsoft applications which use the RDP protocol and VNC sessions. An excellent series of articles has been written on NX at Linuxjournal.com which provides some details as to the actual technical operations.
For anyone who has used VNC for remote GUI control of their systems, NX is far superior!