Welcome to Fight Club! Get physical with your PS2.
I bought this game on its release out of curiosity a few days ago and I've become close acquaintances with muscles I never even knew I had before. Though whether that is from the very physically intensive game or moving all the furniture about every time I want to play it, I'm not quite sure.
First and foremost: ET:K is about working out. Through a number of 'minigames' in four categories (ranging from Fighting Games to the spiritually tinted), ET:K will have you jumping, kicking, ducking and punching all over the room. Despite the wide-angle lens add-on you'll find with the game, you still need to be quite a distance away from the camera (depending on your height, but generally about 3 meters) and you will need a lot of room (say 2m) to either side of you. This may not be a problem for the people at Nike, who evidently sleep in well-lit gyms, but for most of us that means rearranging the furniture every time you want to play the game.
Once you have your personal work-out space, you can start the game. I thoroughly hate navigating the menus by waving my hands so I keep a controller close at hand. Basically, you can either play all the mini-games separately for that quick fix, or enlist in a 12 week program, designed to get you back into shape. My personal favorite are the fighting games. Keep the objects from reaching the center (or yourself) by punching them. The game registers the arc of a punch, so different punches actually do different kinds of damage to the objects that are out to get you. That is, if the EyeToy registers your moves correctly.
Unfortunately, the EyeToy turns out to have a hard time registering your moves in normal lighting conditions. I never owned or even played with an EyeToy before, so I couldn't say if it's because of the extra lens or whether the EyeToy is just an aging piece of hardware. The result, however, is the downfall of ET:K. If the EyeToy can't keep track of your many and sudden moves (as happens far too often), your punches and kicks will not connect. It's very frustrating to hit an incoming ball full force, only to have it breeze past you and into its target. On the other end is the static that the EyeToy seems to generate in dim light. You will have to adjust the EyeToy to even less sensitive to filter out the static, or else your screen will fill up with dozens of pin-pricks, instantly blowing up any incoming objects.
Contrast is the name of the game here. If you have a white wall on the background, wear black longsleeves. If you have the rest of your room behind you, dim all lights in the background and dress in white. Because ET:K has a hard time tracking your mid-tone hands, you might benefit from wearing white gloves or even socks over your hands. Your hands will stand out more and your punches will connect more often.
I actually took this one step further and went out and bought a battery-powered toy lightsaber. I'm sure the boys at Nike would disapprove, but when switched on, the sword is a bright stick on the screen, easily tracked by the EyeToy. A word of warning though: you will extend your reach by another x cm: move the family portrait for the time being because you will strike it across the room in the heat of the fight.
In all, I'm crazy about this game. Though I suspect the minigames and the limited assortment of music will start feeling repetitive quite soon, the combination of sports and gaming was never this intense before. This game /will/ have you breaking a sweat. And you will keep getting back for more. Guaranteed.