Has anyone used one of these?

I have. Not impressed with it either.

The mouse is too large... like seriously large, you need giant hands to use it (the reviews on amazon weren't wrong there, the mouse is seriously huge). The mouse buttons (not the side buttons, but the click buttons on the top) stick when you click them down - you can't click them rapidly because of this. And the mouse is just overall unergonomic as sin. Where your fingers rest on the right side, the mouse curves inward from top going to bottom so you almost have to claw it on the side - combine this with the top edge being, well, an edge that's not very curved at all, and your hand cramps like hell after not long using it. I went as far as using some hard-drying modeling clay/putty to fill in that horribly designed area because i couldn't use the mouse at all otherwise. No problems with the dongle though (the part that goes in your left hand).

As for the software/firmware side of things... yeah, have fun dialing in your mouse sensitivity. It basically won't work at all for Halo (though i haven't tried any other game with it). The inherent aim acceleration and sticky aim they built into the game (to account for using controller analog sticks as input) messes everything up and there's no way of getting around it. Combine that with this: If you dial down for precision, you are way too slow in aiming, if you dial up for more speed, you'll notice your targeting reticle literally jumping across the screen and you have no hope of aiming precisely at all... none. There is no in between and there are no sweet spots - no amount of fiddling with in-game sensitivity or the sensitivy knob on the mouse works, it just doesn't. Believe me, i tried dialing in settings for an entire multi-hour playing session before giving up in the end, putting it back in the box and putting in on my shelf.

And yes, you need a wired controller to use it because the usb adapter that receives signals from the mouse/dongle plugs in between the wired controller and the port, basically intercepting the signals and fiddling with them before sending them on to the xbox for processing.

Great concept... but execution is just bad and leaves ALOT to be desired. I haven't touched it since putting it on the shelf. But here's hoping you have better luck if you decide not to believe me and try it anyway.

As a sidenote, i tried it in Reach btw. Never bothered trying it in H4... i just assumed the inherent issues with aim acceleration and sticky aiming would be present in this game too, so it wasn't worth unboxing it again to find out. Hell, i may just try it again though just to be sure....