Tapulous has revealed that its popular Tap Tap Revenge 3 rhythm game has seen 2 million downloads since its price was dropped from $1 to free on December 23. Silicon Valley Insider reports that the game, which employs both in-app advertising and in-app purchases to generate revenue, did more than 700,000 downloads on Christmas alone, far more than the most current Tap Tap release did last year. Tap Tap Revenge is currently the most popular free application on the U.S. App Store; for more information on the game, see our iPhone Gems review.