Valve's follow-up to the breakaway hit original was due on April 19, but for the last three weeks, the developer has played a deep AR Game.
A long trail of clues hidden in the Potato Sack indie game bundle culminated in a request from GLaDOS herself to lend CPU cycles to her reboot systems.
By clocking up enough hours in thirteen different games, players let the AI out of the bag a few hours early - worldwide.
There is some speculation that the PotatoFool's AR Game may continue, leading up to an Half-Life-related announcement, perhaps at E3.
Ten hours' grace for US players (and a little extra for international markets) might be reward enough in itself, but for the naysayers, there's more.
Those who found all thirty-six potatoes during the AR game have been rewarded with a golden potato - and a free copy of the entire Valve Pack on Steam, which includes Portal 2 itself.
Big Download reports that an interactive trailer for J.J. Abrams upcoming flick Super 8 is available from the game's Extras menu.
Valve's little bonus for PC and Mac gamers didn't go unnoticed by console-centric retailers.
In Australia and New Zealand, where a physical retail release is not scheduled until April 21, the street date has ben broken by major chains and speciality shops including EB Games and GAME - presumably to avoid sales lost to those giving in to the temptation of a quick digital copy.