Was demoing a new app for a client this morning and the State field kept not getting filled in. I had noticed it myself before, but we finally realized why.
You enter your city. Tab. You enter your state. Tab. You enter your ZIP. Tab.
Wait a minute, the state is still empty!
Turns out you have to hit Enter after selecting the state. Then hit tab to continue. This is not the behavior we monkeys have been trained to expect.