I spent a little bit of time K2 on Christmas and I have to say I was pretty impressed. I figure I will start with the negative. The K1 came in a WAY cooler box. The K1's packaging was unique and interesting, it looked like a giant book and while being excessive was definitely fun. I knew the K2 didn't come in nearly as interesting packaging, but I do kind of wish it had. The ones I checked out were gifts and that would have been a nice touch.
One thing I was surprised about was that they went from a mini-USB connector to the micro-USB connector for the end that plugs into the Kindle. Not a big deal, but I was wasn't expecting that and had not seen it mentioned in any reviews.
It feels much slicker with it's thin form factor and light weight. I thought the K2's navigation via the cursor was both better and worse than the scroll wheel. It was nice to have a more accurate idea of exactly what you are selecting thanks to the cursor's ability to actively select stuff vs "line up the sliver dot with the line you think you are on" of the scroll wheel. I did have some problems getting used to clicking the cursor. If you press to the left on a book it wants to delete it. I had a tendency to push "left/down" when I try to click the cursor. I found myself being asked to delete the book rather than reading it a few times in my brief exposure to the K2. That is annoying but I suspect I would get over that tendency pretty quick and learn to press straight down with more accuracy. Text to speech was surprisingly cool, though I don't really have a need/use for it myself...I still think that is a neat feature.
I definitely have a re-vitalized case of upgradeitis, the only thing really saving me from it right now is that I would feel obligated to check out other ereaders too and really think about the DX and how close we might be to a K3 being released. Thank goodness for laziness, occasionally it actually comes in handy.