I use imeem to store my music online, and ugh, it sucks. Not only is it eerily reminiscent of Myspace with its customizable pages, but the service is sketchy at best. Their player works maybe half the time for me.
Needless to say I'm looking for an alternative. One fell into my lap the other day that I'm willing to try out: SoundCloud. SoundCloud is tailored to music artists who want to share and collaborate on the web. It's in Beta right now, but I see some good ideas, including time comments and waveform GUIs. Go ahead and check it out. Here's an example of their player. (Which probably won't show up in GoogleReader... sorry about that).
I also have a couple beta invites if you'd like to join? Just let me know