I did install it from an RDP session. It's a Windows XP SP3 desktop. The install succeeded, but I couldn't connect to the machine. I tried uninstalling and re-installing, but still no joy. Note I must connect to this machine through a Cisco VPN client, and even when I connect to that client I still cannot connect to the machine. I suspect it has to do with security settings on their network, but the client doesn't really have time or inclination to pursue this so unfortunately it's a dead end for me.
I installed a different unattended client on a Windows Server 2003 (SP2) machine, and the install seemed to hang about 3/4 of the way through on the client machine. The install screen went away, and I saw nothing in the systray, and I assumed the install had failed. However, the connection did appear on my SC page, and I was able to connect through that connection, and it worked very well. I was a little disconcerted with the install, as I really felt it should tell me whether it succeeded or failed, but that's just me. This one was also installed via an RDP session.
All in all, I found the concept of unattended installations to be a little on the klunky side, but that's just my perception. I'd probably like it better if there were more end-user feedback (i.e. "Your ScreenConnect client has been installed", or something along those lines). I realize that most times we (the support tech) would be either installing the SC clientside stuff, or we'd be hand-holding the user through it, so it's certainly not a show-stopper.