And if so and you are transferring non-music files, do you need to install any drivers or programs first, or can I just plug the Karma into any random computer and go?

To transfer files between the Karma and the computer, you need the Rio Taxi application, which is separate from Rio Music Manager (but is installed at the same time).

If you do not have Rio Music Manager on the aforementioned random computer, but you happen to have ethernet, then you can run the Java version of Rio Music Manager Lite which also includes a Java version of Rio Taxi. These files are available via the web server on the player itself, so you don't need to download any software, it's self-contained.

The only drawback I can see is that, in order to use ethernet, you've gotta have the dock present. There's no ethernet plug on the player, only USB2 on the player. The dock has USB2 and ethernet.