On the market for an iPhone? Here's a breakdown of all the currently shipping iPhones from Apple.
Google Music and Apple iTunes
Apple's iTunes is amongst the initial merchant partners along with RealNetworks, eMusic and Amazon.com
This confirms a Google and Apple rumor from August 2005 that claimed that "Google is going to offer iTunes somehow on their platform".
The new system appears to be in place (samples: Tanya Donelly, Crash Test Dummies)