I'm just a few minutes into it right now, I love the way that it actually moves with your head...so if you bend your head to the right it bends the camera to the right...that's fucking awesome.
What's funny is the pre-order thing maxed out the second it went on 'sale'. (I'm not sure where the note went, it was first only avaliable by supporting their kickstarter campaign...) http://wiki.teamfortress.com/w/index.php?title=TF2VRH&oldid=1318982 Now you have to pre-order the entire development kit to get the item.