I'd be very careful when considering and implementing most of these ideas. While the sentiment is correct (make users' experience easier), many of these approaches have pitfalls or require fallbacks.

Your signup and login pages MUST be bulletproof.

Autofilling city/state from zip, for example, requires an updated database of postal codes, but users will often consider your autofill city as "wrong", since they use a different district/locale name. Make sure users can override your guesses.