I have one of those and 2 of their Air Music remotes. They are great remotes for the HTPC.
They do provide some functionality for other devices (like TV, AVR, etc.) but you don't get extensive control over those other devices.
However for Media Center, they work great.
The integrated cursor control takes a little getting used to (like a Wii), but once you get it down, it is really nice to be able to pop into a web browser and navigate without having to pull out keyboard/mouse.