As of the Unity desktop, tsclient is dead. What replaces it is Remmina, which is installed via Ubuntu Software Center.
This is crap; it doesn't work. I found that rdesktop works fine on Ubuntu post Unity as well as on Mint.
Below are screenshots. The group, Smack, is an arbitrary name. It could be anything.
Configuring Remmina to make an RDP connection to what happens
to be a Windows 2008 Server on which I'll be running vSphere.
And the advanced preferences tab...
The Remmina main Remote Desktop Client window with one item.
Connecting to the Windows 2008 server...