http://eu.battle.net/d3/en/blog/5691269/Introducing_the_Paragon_System-20_08_2012Here’s how it works:
After you hit level 60, any further experience you earn from killing monsters will begin to count toward Paragon levels
There are 100 Paragon levels
Every Paragon level will reward you with:
Core stats such as Strength, Dexterity, Intelligence, and Vitality in amounts similar to what you’d gain from a normal level
3% Magic Find and 3% Gold Find
In addition, a distinctive increasingly-impressive border will surround your character portrait in the in-game party frame to denote your Paragon progression, with a new frame earned after every ten levels. Your Paragon level will also be visible to other players wherever your normal level is shown
To support the new system, Nephalem Valor (NV) will now also provide a 15% experience bonus per stack, applicable toward Paragon levels. The first Paragon level should take about as long as it took most players to get from level 59 to 60, and the experience requirement will rise from there. The time to reach the upper Paragon levels approximates the long-term time investment required to get a level 99 character in Diablo II.