cortanaMicrosoft has now let Windows Phone 8.1 official along with Cortana. We are bringing it as it happens, so stay tuned!!

Cortana

Action Center

Update lock screen and custom background

Internet explorer 11

Shape writing, which is just like Swype

Word Flow Keyboard which is Guinness book record holder for being fastest keyboard

Incoming calls can be seamlessly redirected to Skype video call with a click

WP8.1 starts rolling out in next few months. For new phones in April end /  Early May

Universal apps. Buy apps once, use for both Windows Phones & Windows devices, great news!!