Spent the whole day at work with the DK2, my first impressions:
Pros
+Cable setup is way easier, even with a webcam now.
+Headset is more "solid" in appearance.
+Screen colors and blacks are fantastic, as expected.
+The resolution difference is huge, I read that some people find it almost the same, nonsense, the upgrade is big.
+Latency is almost non-existant, and due to that, i can play way more time with it, now I'm really starting to feel like I could play an entire game with the Rift.
+Head-tracking works, and it's mindblowing, really impressed.
Cons
-Software and drivers are a mess, tried with different computers, different setups... service crashes sometimes, direct mode doesn't work, extended mode works in a strange way, I can't duplicate the desktop, I have to extend it and make the DK2 the main display, so I have to use the distorted destkop to launch anything, the screen starts by default with a 90º rotation...
-Black borders, in some demos more noticeable than in others. This is an issue I never had with the DK1, I don't know if it is the FOV, the smaller screen, or the bigger lenses, but I hate it, it's the worst problem of the DK2, sometimes it looks like you are looking to a virtual screen with the demo playing, instead of feeling inside the demo like with the DK1.
I suppose with the weeks the new SDK will solve a few of this problems, mainly the software and drivers one, not being able to use the direct mode is a bummer.