I've got to say, I was dubious about how useful an instant messenger service would be on the Xbox 360, but Microsoft has got the implementation just right with the Messenger Kit. Being able to drop out of a game and just send a quick note to someone, without having to go through the pain of moving a cursor around a virtual keyboard is quite a revelation for a console. Yes, I know that PS3 owners will be moaning about how you can use a proper keyboard with Sony's console, but quite frankly, I don't want a proper keyboard plugged in just for short messenger chats. The fact is that most of my team keep in touch over MSN, and now if something really important comes up and I'm in the middle of a Bioshock session, I can simply hit pause, reply and get back to Rapture with minimum fuss.
At £25, even the price of the Messenger Kit is impressive, taking away a potential barrier for end user uptake. A couple of the guys in the office have even said that they'd consider buying one, and recommendations don't come much higher than that. If there's a down side, it's that you can't seem to get a black version just yet, so anyone who's bought a nice new X360 Elite might be put off - I'd be surprised if a black version didn't appear though.
For me, the Messenger Kit goes down as the best Xbox 360 accessory available. It really does improve the functionality and usability of the system. It's surprisingly simple to use and the implementation within the Xbox Live environment is seamless. Microsoft's console definitely seems to be on a winning streak right now!