Fortunately, I decided to try it before I needed it, but I am unable to connect to my work's VPN using Windows 8.1. I will explain what has happened so far.
The connection I make is a web VPN type connection, and the url I connect to says "Cisco Secure Desktop" in case that specifies a specific type of Cisco software, as there seem to be at least a couple of different Cisco VPNs.
When I first connected, I received a message that I needed to upgrade Java. So, I did. it loaded successfully, and the Java site confirms I am running the latest version. Apparently the ActiveX method doesn't work, since it is bypassed. (Maybe I should tinker with ActiveX settings??).
Now, I get a little further... When I attempt to do an RDP connection, I get an error indicated an improperly signed applet, and when I select to ignore, nothing happens anyway.
In searches, I don't really see any solutions that make sense to me. When I follow links, I get to pages describing an array of problems and solutions with Cisco VPNs on 8 and 8.1, but they reference products that don't seem to match what I am using.
I will continue to look, and post any results here, but I am curious if anyone has had any success in a similar connection with 8.1.