Gizmodo has posted a leaked video of someone playing Half-Life 2 using Microsoft's Project Natal.
It's not yet clear whether the video is authentic but seeing it in action, and actually working, is definitely a nice step forward if genuine, one can't help but notice the strange hand motions that are being made to make the game playable. The hand motions also don't seem to work too well in some instances. You'll see, a little over halfway through the video, the guy has issues interacting with an object.
Microsoft is, without a doubt, doing a lot of internal testing with different games like this, but at some point they are going to have to decide if Natal is practical enough for mainstream gaming. First Person Shooters require a precise level of control with minimal lag. Natal's potential for accuracy and ease of use is something to get excited about, but the lag factor and problems differentiating hand motions may pose an issue for hardcore gamers who can't afford mistakes.
You can see the video below. Gizmodo stresses that the video's source is unconfirmed and it should not be viewed as a final gameplay video. It's most likely an early beta or a proof of concept.