So, here's my worry with all of this:
MusicMatch uses WMA. I'm guessing that will basically be true for all music stores released from here on out besides the Apple iTunes music store. People here have argued that:
iPod is the most popular MP3 player, therefore, people won't download WMA files.
Hrm. To me, this could just as easily go the other way -- the iPod can be seen as a niche toy that only supports a proprietary format. (which, of course, isn't true -- WMA is the proprietary format, not AAC) If online music downloading becomes more popular and common through the us of these services, unless EVERYONE uses iTunes music store, people will be upset they can't play their songs on their iPod.. and I'm guessing they'll blame Apple for not supporting WMA, not the other way around.
Plus, another problem nobody has mentioned is: what can you use AAC with on a PC *besides* iTunes and QuickTime? Folks, if you're offered music stores that allow downloading of music that will work seamlessly in your home movies or your slideshows and even in your pro audio apps, vs. a format (AAC) that *only* plays in one particular MP3 player, you will clearly pick the first one. It's just common sense.
Basically, here's what Apple is offering to PC people: A cool MP3 app called iTunes and the ability to download music that will play within that app, burn to CDs, and work on the iPod. It will only work on the iPod, not any other MP3 players, and it will play on your computer, but only in Apple's own app. So, while some people may like iTunes, there are a lot of people who still want to use their favorite MP3 program, and the fact that iTMS only uses AAC may be enough for people to steer clear of it entirely on the PC side.
I don't think we'll be seeing 9 times the sales when Apple releases iTMS for Windows, unless they've got something clever up their sleeves... I'm just worried we'll see the downfall in popularity of the iPod and the downfall in popularity of AAC. But I'd love to be proved wrong.
Here's to hoping iTMS for Windows is taking a long time to be released because they've got something new in "store" for us... (haha, sorry, I couldn't resist)