And I'm another advocate for Google Play Music....
I assume you all heard that Amazon is giving back digital copies of every CD purchased from them since 1998 (15 years!) as long as they have the license to do so for any particular album.
I haven't purchased many CDs from them since '98 -- about 30 total, but they've already added about 15 of those albums to my Amazon Cloud Player. I've downloaded those all to my desktop, and then Google's Music Player automatically uploaded them to my Google Music account. As long as Google Music knows which folder to look in (you set this up yourself), it will automatically upload any new music it finds. It was sweet how slick it all worked.
So now I have those 15 albums (and Amazon says there are more to come, they just have to work out the kinks) on Google's cloud to play on my N7 whenever I want.