I am looking at connecting to a openSuse 11.1 Beta 3 virtual machine from my Vista 64-bit development workstation. I found UltraVNC Viewer to be the only option for this purpose. Is there any other clients that I can use to connect from Vista to openSuse/other Linux installs?
Note: Bandwidth is not a worry, the connection will be using a Gigabit network.
I don't know about Vista but I have successfully used X-Ming on Windows XP to talk to a Debian box.
I will double Adam's suggestion to use XMing. You can also enable X11-Forwarding in SSH and use, say, PuTTy, to open up different X applications running on the SUSE box (this, if I remember correctly, requires some sort of a X server to be running on the Windows box, and for which, I have been using Xming.
That aside, I've used tightVNC before to export X displays on Linux boxes over to Windows.
I successfully used both VNC (with UltraVNC) and XMing to access GUI sessions from Windows on a Linux box. You can find a detailed tutorial about setting up Xming on my blog. You could also try xrdp if you for some reason need to use the RDP protocol.
I have been happily using NoMachine NxClient on windows, conecting to nxServer on a suse linux box. The lag is minimal, feels very fast. Sessions can be only suspended, which adds to the feeling of speed.