I came from the Rezound. After I bought the S5, I made a call to my wife, and she immediately noticed the difference in call quality. I was so fed up with my Rezound that I was ready to get the new one.
I have noticed that when using my earbuds, the volume is a little low, but I can deal with that.
The battery life is like my rezound with the extended battery in. It's much bigger in the hand (the only downside for me). I seem the have similar or better signal. Also just new phone snappiness. Head phones seem as nice a the beats ones (which now after several years are beat up)