My first experience with type of architecture was in the 80's with something called an "X terminal". All the same elements, a machine with a display / keyboard /mouse that had a network protocol to talk to some hardware acting on my behalf in a machine room. I could sit down at any station and open up my desktop, just as I had left it. It is a pretty decent experience even with only a 10mbit Ethernet network.
The second time I got to experience this architecture was in the Citrix days (late 90's early 2000's) Now the OS was always Windows and the network protocol was proprietary, but you could bring up an entire enterprise without all that pesky installing/rebooting that was the life of an early Window's system administrator. Also gave you control over employees trying to put bogus software on the computer. No Netscape Communicator for you! Work work work. :-)
Somewhere after Citrix imploded with all the problems that come with a walled garden with razor wire on the walls, we started seeing deployments using virtual machines and VNC. That gave you the "what you see is what is happening" feel of Citrix but now you had a different choice of operating systems and better vendor flexibility. VNC over a SSH SOCKS proxy replaced X11 over SSH as a more "universal" way of implementing this architectural design pattern.
Of course Google gave us "the browser is the computer" with ChromeOS and now the machine as a browser target where the browser is something more standard.
I like the architecture but in the previous iterations there was always some big problem it was addressing, X terminals addressed mobility, Citrix addressed enterprise configuration management, VNC/VM addressed multiple OSes other than Windows while retaining enterprise configuration management, and ChromeOS went for a better security model, mode-less configuration, and minimal cost of entry.
What problem does Workstream address either better or differently than what the above solutions address/addressed?