Yes, there seems to be (are) issues with the Sprint Note 3...
I have one and the four problems I have are:
1. The voice quality you noted. I have read other carriers are have this problem too.
2. WiFi dropping out when you have any weak signal.
3. Poorer signal then other phones. I am comparing it to my Note 2 (on Sprint).
4. Google Services eating my battery at night.
All have threads here on this board.
What is so frustrating is that the first 2 are intermittent.
The last 2 are items that I can live with.
Sprint acknowledges the voice problem.
Now I LOVE my Note 3!!!! I use it for more than a phone, it has so many great features.
I could still exchange it as I am right at my 14 day period but it is a royal pain in the pants to reload and set up my Galaxies. (You know the little things).
I am happy that I got on the band wagon early.
Good Luck on your decision.