This was the big announcement heralded by the 1984 commercial spoof, according to TechCrunch, and 5 million songs are currently available... to some.
Unlike iTunes, doubleTwist with Amazon MP3 support is Mac and US-only right now (not that Amazon MP3 is widely available anyway -- what gives Amazon? You've been promising more for a long, long time now?!) with a PC version coming soon. US users, especially those who have many different devices, with non-Apple devices in the mix, may want to take a serious look at (we know Palm should!) And let's face it -- iTunes needs the competition!
If you're a doubleTwist user, let us know what you think of this new version.