Fast and responsive UI rather then flaunt and animated.
I have played for a while with the demo of the components.
What I noticed is that components with popup elements, such as ComboBox, DatePicker, TimePicker, ... have a small but visible delay, which becomes quite annoying with time.
Look at ComboBox demo, it seems there is some delay due to pre-configured animation effects on the control. In slower browsers (take Firefox 6.0.2) the delay is obvious.
The support for animation in general is a cool idea, but in most business applications it is not welcome by users who use application on a daily basis.
Personaly, looking at the demo I am not sure if I can rely on kendoUI if my application designed for "do the job" rather then "enjoy UI".
I think it would be very nice if the demo has settings to disable all animations, to run it at full speed and demonstrate rich AND really responsive UI.