Pros: Works right away in Win 7/Win 8. No drivers required.
Cons: Joypad is a bit sluggish; IR sensor has distractingly bright red LED
As a mouse, the joypad is a bit sluggish. You can speed it up somewhat with the Control Panel Mouse applet, but that can make it tough to position the mouse pointer precisely (e.g., for resizing windows by dragging their borders). But it's fine for occasional use and it avoids having to keep an actual mouse attached to the PC.
Aside from the joypad, the remote keys emulate keyboard keys, which limits its usefulness in other apps (unless they happen to use similar keys to WMC). And the IR sensor has a red LED that blinks brightly when you use it. That lets you know it's working but can be distracting.
Bottom line: it gives WMC that "appliance" feel for a very low price.