My observations after a little over a year with the A20: I'm a fan. I haven't noticed any tendency to get heavy, and I do some fairly long legs. That observation should be tempered by the fact that I also was fairly tolerant of the dreaded David Clamps.
Yea, as far as I have been ale to tell, the Bluetooth is only for cell phones. I read the manual pretty thoroughly researching this point exactly, and that was what I took away form my reading. However, I haven't ever taken a Blue tooth enabled music player and attempted to connect it.