So...I have a 32 GB iPhone, and Mac apps take up WAY more memory than Android (that's what makes them faster, they're not compiling). So I didn't have a lot of room to put my music.
Maybe everyone else knows about this, and I'm like George Bush discovering bar codes, but the Google Play Music app lets you store your music library on the cloud for free. I think the limit is 100,000 songs or something like. I think the way it works is that if they have the music stored already, you just stream that, you don't actually "upload" your music unless it's not on their server.
This is great!! I've already uploaded a ton of stuff so it's available when I go for walks.
The one wrinkle is there are two different apps, Google Play Music and another one (which I believe is older) called Music Manager. I find Music Manager easier to use, more reliable, and it accepts WMA files. It may just be that Music Manager is better about indicating your upload progress, though...I'll be looking into this more.