I have two N900's ATM and both have the best voice call quality of any "phone" I have used- including G1 and Droid (have or had them too).

My issue with both N900's for phone function is weak reception in low signal areas and slooow reacquisition when signal is lost, on both N900's. Others are having great reception, so great for them

I would gladly trade some of that crystal clear quality for better recption in low 2G areas