IGN posted an article in which Jay Wilson provided some more details about the upcoming Infernal Machine and Monster Power systems in patch 1.0.5.
"The goal of the system is to allow players set a monster power level, and the higher they set the level the bigger the bonuses they'll get to magic find, experience and loot drops -- but the harder the game will be," Wilson told IGN
"At level 60 players can find various objects to put together a device that will allow them to fight more powerful bosses hidden throughout the game," said Wilson
Completing the Inferno Machine can apparently net you a legendary ring acquirable only through this event. -IGN