1) Multi-core processor support
Windows Phone 7.5 was limited to single-core processors. With multi-core processors becoming the norm, this move will help Windows Phone based phones compete with the Androids and iPhones of the world.
2) Bigger, sharper screens
Windows Phone 7.5 maxed out at 480X800 (WVGA) resolutions. Windows Phone 8 supports two new screen resolutions - 1280x768 and 1280x720, opening the door to 720p displays.
3) MicroSD card support
Windows Phone 8 comes with MicroSD support, so users are no longer limited by the built-in storage.
4) NFC wireless sharing
NFC, or Near Field Communication, technology enables devices to communicate with each other over radio frequencies without any physical contact (much like Bluetooth). Windows Phone 8 comes with built-in NFC support that lets you share information (like a contact) with another NFC-enabled device.
5) Internet Explorer 10
The next version of Windows Phone comes with the same web browsing engine as Window 8 PCs and tablets. IE10 is faster and more secure, with advanced anti-phishing features like SmartScreen Filter to block dangerous websites and malware.
You can keep debit and credit cards, coupons, boarding passes, and other important info in your Wallet. Paired with a secure SIM or NFC, it can even be used to make payments.
7) Nokia Maps
Maps in Windows Phone 8 will be powered by Nokia and will offer turn-by-turn navigation in several countries. The ability to store maps offline so they can be operated without a data connection will be a nice plus.
8) Revamped Start screen
New colours, user resizable tiles mean that the start screen is more personal than ever.