Rovio tweeted "10 in 10:-)" yesterday, which was later confirmed to mean they sold had 10 million copies of Angry Birds Rio downloaded in 10 days. Confirmed because someone tweeted at Rovio if this was what they meant, and the reply was yes...
The downloads (free and paid versions) appear to be across both iPhone and iPad platforms, and given that the iPad version is $2.99 and the fact that the game still sits at the #1 spot on both of Apple's app stores, that results in a ton of money.
I picked up the first game when I finally gave in and got an iPod Touch for gaming recently. And while I thought it was dumb at first, after about 20 of the more basic levels I've grown to enjoy playing a level once every few days or so. But, I don't know if I really need more Angry Birds in my life.
Apparently 10 million other people did.