Applications and games can now use the entirety of the display with 4.4, meaning no more notifications bar and no more battery icon. Just full screen applications and games. Android’s UI now stays hidden whenever you’re interacting with content.
Android 4.4 will run on handsets with just 512MB of RAM. That’s right, people: KitKat will theoretically run on the HTC Wildfire S that came out almost three years ago!
Smart caller ID
KitKat takes things further. When you receive a call from an unknown number ,like a business or a courier delivery guy.For instance ,KitKat will scan Google Maps for an appropriate image and, if it can find one, use it for the caller ID. The idea is to give you a better idea of who is calling you.
Hangouts is the new SMS app
Google has re-purposed its Hangouts application to feature SMS and MMS messages, as well as IM threads from your Google contacts.
Screen-record is one thing ,having the ability to capture real-time video of what’s happening on your droid’s display is another thing entirely. With Android KitKat this is now a reality, and all saved content is stored on your device as an MP4 file.
Other small changes are ,
• No more Blue in notification or anywhere , its replaced with white .
•Transparent notification bar etc..
• Cloud print.
Source : KnowYourMobile