Oslo
I was going to write a large post on Oslo, until I found this one. I still did not play enough with it yet to add value to what Fowler said.
As I guess everyone in the world is waiting to listen what I have to say about it, I'd just say that I liked it, and that it's probably the most exciting piece of technology I've seen during the PDC.
I still have a lot of questions that I'll try to answer by reading the book, playing with the bits, and trying to grab some Oslo guy during the breaks.