I wore the S305 for about 70 minutes while walking this morning. The sound quality was acceptable for non serious listening and they were comfortable for me. I could see how someone with a larger head might find them too tight, as they were slightly tight on me. I called my wife and she called me while listening to music to test them and they worked fine. Of course, voice dialing does not work, as that is a Droid issue. Holding down the call button for 2 seconds did dial the last number dialed. Music resumed after ending the call.
I think they would work for jogging, but I did not try that. I would have if I had read the last post earlier. I'll go downstairs on the treadmill and try for a couple of minutes.
OK, I'm back. I ran at 5 mph and 6 mph and they didn't move around at all. For reference, I just measured my head for hat size and I'm between 7 and 7-1/8.