Quite a few people use Kinect with VoxCommando and I believe some people are very happy with the results they get.
I personally found that it did not match my expectations. In terms of noise-cancelling I found it to be not very impressive. Your voice can be picked up by the microphone from pretty far away which is nice but it really picks up a lot of other sounds too. In this sense it is not too different from a boundary layer microphone, except that the Kinect audio quality may not be as good. I found that in terms of audio quality, my Kinect was poorer than most other microphones that I have tried. This might be down to quality control. I get the impression that some Kinects are better than others and it is possible that I just got a dud.
So, yeah it works fine, but the same can be said of many other microphones that cost less. Once you try something like VoxWav or an Amulet you get used to the idea of being understood correctly almost every time, with essentially zero false positives, and it makes the Kinect experience seem a bit pale by comparison.
If you have a Kinect or can get one cheap, then by all means give it a shot. Maybe it will be the perfect solution for you. Just be prepared for the possibility that it isn't going to be all that you had hoped. I for one did not feal that it lived up to what it promised, despite the fancy specs.
I suspect that there are other array microphones that perform better, but even the expensive ones still don't really filter out other sounds that effectively while still delivering clear audio.
Personally, I still prefer using an Amulet, VoxWav, or a wireless headset, but VoxCommando is all about doing things your own way so try different things and see what works best for you!