Remote desktop viewer is basically a launcher that lets you choose which
protocol to try, as long as you have the proper programs installed. But
it looks like they changed the default program for that. In ubuntu 8.04
"remote desktop viewer" launched "tsclient" but in later ubuntu releases
it appears to launch "vinagre" which left a sour taste in my mouth.

I prefer tsclient over vinagre because it's more stable, and seems more
reliable. tsclient lets you choose either vnc, rdp, rdpv5, xdmcp or ica
to connect.