If you haven't read the patch 1.04 preview for the Paragon system, check it out here. Most of the relevant information in that article can be found directly below "Introducing the Paragon System". Those bullet points are the bare bones of the system, such as how Paragon levels are gained and what effect they have on the character. Basically, they add Gold Find, Magic Find, and a little bit of the base stats to your character, as well as giving you a slightly cooler looking portrait every 10 Paragon levels.
Jay Wilson went on to talk about the length of time involved in acquiring the levels, and the solution to the magic find item property issue which has been bugging the community for a while. It should take roughly the same amount of time that it takes for a level 1 Diablo 2 character to reach level 99. This means that reaching Paragon level 100 will take several months for most people.This ties in nicely with the solution to the Magic Find problem.
There is going to be a cap of 300% Magic Find and Gold Find in 1.04, which does not include Nephalem Valor. At Paragon level 100, the player will naturally reach the cap and only gain a further bonus from Nephalem Valor stacks (reaching a maximum of 450% Magic Find and Gold Find) instead of from items.
This will help phase out the highly priced Magic Find items on the AH very gradually. A sudden shift could have resulted in economic turmoil. Over the next year, expect Magic Find gear to be phased out of the top tier items as players gain more Paragon.