First a pre-warning, if you are Jailbroken DO NOT UPDATE to iOS 4.1 when it arrives until you are given the all clear.

iOS 4.1 will bring the following features.

Proximity Sensor Bug Fixed

HDR Camera Software (Much better quality photos)

Game Centre will be released!

iTunes new Social Networking called PING

TV Show Rentals

HD Movie Uploading

For more details visit here