Just got a chance to try out the Xbox One at a local Microsoft store this afternoon after work. There wasn't a line behind me, so I got to try out both Killer Instinct and Forza 5, but I didn't want to spend a lot of time there before heading home for the day, so these are just some quick first impressions with the hands-on (and I didn't spend time messing around with the UI).
The controller felt...well, it felt a lot like a 360 controller. It was comfortable, and I didn't notice any glaring problems. The sticks didn't feel any worse for being slightly smaller or slightly looser. The bumper issue that people have complained about shouldn't be a problem for me since I don't have particularly large hands; there seemed to be enough space for me to press the bumper when I needed to. Again, these are just my quick impressions, I didn't have the opportunity to spend hours putting the controller through its paces.
Killer Instinct looked good, and I wasn't very good at it, which was what I expected since I have very little experience with fighting games. I figured out how to do an Endokuken, at least. I'm still looking forward to downloading the free stuff and trying out Dojo mode, to see if this is a game I could get into with enough practice.
Forza (another game I'm no good at, since I'm not that good at racing games) was very pretty, and the rumble triggers felt cool.
Overall it was a good experience, I had fun and I am excited to get mine sometime next year, hopefully in February or March.