Re: Improvements with 4.4?
In addition to the above:
You can now set a default SMS app from settings->more (under wireless & networks).
If you have more than the standard Motorola home launcher, you can set the default at settings->home
Tap & pay has a setting. I've never tried it (and never will) but I understand that it allows Google Wallet tap and pay to work.
There is better support for Bluetooth LE, and devices like the Fitbit devices now work with the Droids.
If you have two apps that can do something, with nothing set as the default (say, two browsers on the system), the first time a browser link is pressed a list of items is shown, allowing yo to choose one and choose a button that says "Just once" or "Always". That's not new, but what is new is that if you select something and say "Just once", that item will be highlighted the next time you have the same choice.
There is a full-screen mode for apps that support it. The first time you see it it tells you that you can return to normal with a swipe down from the top.
There is now a settings->printing setting; I have printed from GMail, Hangouts and Chrome.
I believe that the stock keyboard supports emoji (or more emoji.) I'm not 100% sure which - I don't use the stock keyboard anyway.
Otherwise, a lot of improvements under the hood. And perhaps things that I have not noticed...