Hey ricardobeat, Grooveshark developer here. Thanks for the support! It just so happens that we're currently making an effort to reach out to users who haven't been back in a while to find out why and see if there is anything we could do to improve the service. If you'd like to contribute your thoughts, just shoot an email over to support@grooveshark.com
I spend about half my time in other music services (Turntable.fm, Last.fm, Spotify, etc.). What I would really like to see is better playlist import/export capability. For instance, I would love to have the same songs available whether I'm spinning in Turntable or just playing music for myself.
I realize that by the nature of the problem, you can only fulfill half of it. I also know that it's probably a pipe dream since lock-in is so valuable, but that is what I would really like to see from my music services.
Thanks for the feedback. One of our other developers created http://groovebackup.com/ to make exporting playlists easier. It's not officially supported, but it should get the job done. :) Another dev was working on playlist importing as a side project but I think it fell by the wayside.
Thanks!