I'm not entirely certain how beneficial it is to have DRM free AAC music from Apple if the 3rd party players out there CANNOT play the tracks Apple is selling. Both my Nokia phone and my JVC car stereo with USB that both support non-DRM AAC will NOT properly play most Apple DRM free AAC tracks. They either won't play at all or play with really weird distortions (like the pitch constantly varying up and down). The AAC tracks I have encoded myself from CDs play just fine on those players and I use 256kbps. If I "convert" the Apple tracks to 256kpbs (I know it sounds ridiculous since that is what it already is) then they DO work just fine. The problem there is that any time you convert something already compressed, it will only degrade more. Plus this is a pain in the butt to have to convert everything I buy from Apple. I might as well just buy an MP3 from Amazon in that regard since I use my USB port in my car all the time (I have an 8GB micro USB stick that works great) and I often use my phone as well when at work and so I need to load them up with songs from my library.
After the last iTunes release which has an "iTunes Plus" setting, I think I finally know WHY the Apple DRM free tracks don't get along with many 3rd party players. I think the problem stems from Apple using a variable bit rate with its 256kbps AAC files. While this is pretty common for MP3s these days and most players out there now support it for MP3s, I'm guessing AAC support is much more spotty even on devices that claim they support it and both my phone and my car stereo probably do not support variable bit rates on AAC files. Because up until recently there was no user setting for a variable bit rate with AAC, that would explain why all my encoded or converted files played fine since those players support fixed bit-rate AAC just fine. Now that there IS a variable bit-rate option, it's easy to see that is what is causing these players to not function or act strange.
Of course, you can blame all the 3rd party players since they should be supporting variable bit rates and I'm sure now that DRM free is the norm, things will improve over time, but that does not solve the standing problem that all my 3rd party AAC players do not like Apple's DRM free tracks one bit, which means any purchases I make will have to be converted to fixed rates to be usable with those players.