I could be wrong, but I thought WMA (like some of its WMV siblings) was a bastardized version of the AAC format (or some other open standard format) that Microsoft "proprieterized". Can't seem to find info on that right now
I hate to say it, but WMAs can sound fantastic. I'm working with a client now who is sending me WMAs, which is really irritating cuz I have to jump through hoops to convert them, but anyway, they sound great. Of course, high rate AACs sound great too. I have yet to do any thorough comparisons. Suffice it to say, they both sound good to great depending on the encoding.
As for playing WMAs on the iPod, I was originally going to make a strong case for saying yes, but then someone pointed out that there are other options besides iTunes for WMA DL-ing, which would be a disaster. iPods are just the "in" for iTunes. Apple wants to sell iPods, sure, but that's just the beginning. It's really about iTMS. A perpetual cash cow. Now if Apple could somehow allow non-iPod technology to work with iTMS, that might be a sacrifice worth taking in the long run.
Or maybe not, what do I know? So far, Apple has made very good decisions (as of late, not in the early years, but we won't go there), delivered great products and done extremely well under dire circumstances. They should keep doing whatever they're doing that's got them this far.