OK, so EMI's music is gonna be on iTunes without any DRM. Huzzah! But it's AAC, albeit unencrypted AAC, not the more friendly and universal MP3 format. While many players support AAC, not all do.

Currently, Microsoft, Nokia, Sandisk (the e200 line) and Sony already support AAC playback on their DAPs. However, Sandisk, Creative, Toshiba, Cowon, Philips and others will leave you SOL until they release firmware patches. But don't worry, they will. There's sure to be tons of firmware patches on the way for any player that can't play unencrypted AAC files; it just might take some patience. Keep your eyes peeled, and make sure your player can handle AAC's before taking the plunge into legal DRM-free music downloading goodness.

Will Your MP3 Player Support Apple/EMI's AAC Files? [Gadget Lab]