Both the Wii and DSi can play the format iTunes currently uses. I think the PSP and PS3 can as well. I’m also pretty sure Archos and a couple other of the high end media players also work with AAC. AFAIK, only the low end stuff, like SanDisk’s fare, are still using silicon tied to MP3/WMA.

Isn't AAC an open standard?

Yes, although the silicon was slow coming. For a while, the iPod was the only game in town. The few other devices that used AAC at the time (like a Sony 8cm CD player I used to use) used the older MP3 style container instead of the modern MOV/M4A wrapper.

You know, I can't remember the last time I bought a DRM track from iTunes, and trust me, I buy a lot of tracks on iTunes.