Here are a few of the new features in iOS 4.3:
1. From now on, you can share your Hotspot in iPhone and make your iPhone a Wi-Fi router:

2. AirPlay for all the third party apps:

3. A new icon for FaceTime:

4. iAd full screen banners:

5. A new feature for iPads named multitouch gestures. With this new feature, iPad doesn't need to have the home button anymore:

6. A new option in iPad for switching between mute and rotation lock:

7. A new font (Noteworthy) has been added to iPad Note.
8. You can set your idevice to repeat message alert up to 10 times:

9. A new feature named Photo Booth might be added to 4.3. You can add effects and edit pictures with this new feature:

Sources: Redmondpie 9to5mac
10. In analyzing the system data/files of iOS 4.3 it has been noticed that Apple might announce a new service named Find my friends. We still don't know if it's gonna be a free service like Google Latitude or it'll be specifically for MobileMe users (In the last months of 2010 Steve Jobs, as an answer to one of the MobileMe users, said MobileMe will be quite better in 2011. Probably this is the first step of "revolutionizing" MobileMe )

Source: engadget
