Like the concept, but it violates Fitts' law. ( http://en.wikipedia.org/wiki/Fitts%27_law )

I don't want to make precise movements with my mouse. Buttons should be large and margins between buttons should keep me from accidentally clicking the wrong one. The time picker fails on both counts.

Also, first picking AM/PM before you pick the hour is confusing. Add to that that the control is huge, so it wouldn't fit in any normal web forms.

Good exercise in UI design, but I hope no web-app will ever force me to use it.