Good question. I was wondering the same thing. It looks like using a task killer is the only answer. But maybe when you pause it and back out, it doesn't use any battery or memory? I don't know.
On a side note, does anyone know of any solid music player apps? I'm actually quite impressed with the built in htc music widget. My only complaint about it would be that it's kind of bland looking. I'd like to customize it a little. Ideas anyone?
And also the maximum volume isn't very loud, but I'm sure that's the eris itself, and not the app. The overall sound quality is good, but not as good as my little nano. But I didn't expect it to be.