Some quick impressions of Kitkat so far:
+ The no black bars in the status bar and nav bar when in the homescreen is pretty nice looking
+ Homescreen with the Google Now stuff looks pretty good too
+ The clock doesn't look ugly anymore now that Google got rid of the bolded font
+ I like showing more information about battery drain from apps that use location
+ Bigger focus on Google Now.
+ It looks like more control on Google Now too like adding reminders and easier to modify preferences.
+ Easier and more apparent way to open Google Now and Camera from the lockscreen
+ Easier to choose a default Launcher now that it's in the Settings
- The white font when not in the homescreen (the black bars return) make apps look really plain and bland.
- Moving to neutral colours for other apps like the Keyboard make it looks plain as well
- I'm not really liking the changed Roboto font
- Tougher to add screens and widgets
- Dialer's design is all over the place. It has a new interface but then it looks the same when calling someone. Can't comment on the Yellow Pages thing since I think it's not working on this build.
I can't comment on the NFC part because it doesnt seem to work on this build.
Anyway, yeah, the bland, grey colours are really bothering me. It looks very soul-less. Maybe I just need to get used to it.
EDIT - It also looks like Google got rid of lockscreen widgets in 4.4