Both the keyboard and mouse use the same receiver dongle:

...which is not only quite tiny but has a helluva range -- I've had the keyboard work from up to 30 feet and the mouse from 25, and these are when the receiver is plugged into the back of my PC or XBox, both of which are in a corner.
Both the keyboard and mouse take a single AA battery, and the battery life you get out of both pieces is amazing. The keyboard has survived on a single battery (one of the generic, cheap, gold, Japanese ones that comes in the box with the unit, no less) for about 250 hours. The mouse is a little harder on its battery and can only last about 2/3 as long as the keyboard, but 165 hours on a single cheapo battery for an optical mouse isn't too shabby. These figures are considering, though, that I take the batteries out of all my electronics when I don't use them (as I discovered long ago with a flashlight that leaving batteries in the item depletes them) and that I used both items 11 hours a day, one day a week at my college. This same fact is also how I broke both battery covers so quickly. When I say broke, I don't mean functionally broken, only aesthetically. Somehow these covers, despite the keyboard's cover missing half of the clip and the mouse's broken in the middle, manage to stay on and hold the battery in.

The keyboard has started to warp slightly from use in my lap, though:

It's not particularly serious as its function has not been impeded yet, but I worry about the problem becoming worse in the future.
Many people I read reviews from seemed to dislike the shape of the mouse, but I find no problem with my hand contouring to it. Then again, I have gigantic hands and I'm a middle/ring mouser, so it fits pretty neatly into my palm when I use it:



Next is my X31 headset. For the longest time I agonized over dropping a hundred clams for a gaming headset (as anyone on my MSN list could tell you) but I ended up getting it for three reasons: 1) the TV we have is a 27" CRT from 2002 with two three-inch speakers on the front of the unit, and the concept of stereo was foreign; 2) most of my gaming is done after everyone's gone to sleep; c) the remainder of my gaming was consistently drowned out by mindless chatter amongst my family, or other equally as annoying occurrences (appliances, music from the PC speakers (I seem to be the only person who likes to use the headset), dogs, so on so forth). After getting Garfield off MW2 for a few minutes, I got him to pose for a vanity shot:

I'll admit outright that the headset is mildly bulky, but is not heavy at all. The earcups also don't crush your skull but still stay firmly secured to your head.
The third button from the left enables sound output effects:

And they are bass boost and stereo widening. Bass boost is obviously very cool for explosions and gunfire, and stereo widening is exceptionally helpful when you need to know exactly what direction something is coming from. Because there's just the two earcup speakers, discerning between, for example, directly behind you and behind-but-slightly-to-the-right is difficult without widened stereo. You have the option of turning either on individually or having both on at once.
This headset uses digital RF for an amazing sound that shows no discernible latency. The transmitter is a tiny unit that weighs less and takes up less space than the USB cord it uses for power (you plug it into a USB port on your XBox to power it) and the transmitter itself is smaller than a playing card:

There are only two notable downsides to the X31 headset. Firstly, and most annoyingly, the fabric used on the ear cups is not colourfast. What does this mean? The black dye from the fabric came off on my head. For several days after I took off the headset, I'd have purple ears and a purple ring all the way around them on my head. The second item is listed as a feature on the package -- the "battery extender circuit". As labeled: "never suffer diminished performance from a weak battery". What does this translate to in plain English? The headset dies with no warning. You'll be happily killing your friends in multiplayer and you will suddenly be devoid of sound, and I can assure you that rushing to swap batteries before you offer a free kill in the midst of a deathmatch is difficult.
NERD.