I got to try it out. First off, it's amazing. I was going in with big expectations and it didn't dissapoint. I only got to use it for about half an hour and only tried a space shooter type game and the tuscany demo. The space shooter was a lot of fun. It was basically just a dog fight in space. You move around with the controller and use the rift to look around. It felt very natural and was a lot of fun. The tuscany demo is amazing. We had the razer hydras hooked up. Basically you just walk around a villa and interact with items. For example there's a basketball you can bounce and throw around and some books and logs you can throw in a fire. It's a bizarre feeling because you really feel like you're there.
There were problems though that should be ironed out before the retail version. The picture is very low res and goes out of focus quite a bit. It's not a good looking picture. It also blurs quite a lot if you move your head quickly. The biggest problem for me is that it doesn't track when you lean left or right. Everyone that tried it felt sick. It's playing with your senses and when it puts them out of wack you really feel like ****. I had to sit down for a couple minutes to recover.
It's comfortable and didn't give me any problems with anything like that. I'm really excited for an updated version. 1080p with better head tracking is going to be amazing. I'll be shocked if Sony or MS aren't all over this in the future. It really is like nothing I've ever experienced. Playing a game like Skyrim would be insane.
Here's some pics of what you get in the dev kit and how the picture looks running through a regular monitor.