I just traded my 2002 LS Sport for a 2009 MKZ with Ultimate Package which includes Navagation and Sync. I am still trying to learn how to use sync effectively.

I did tutatorial last night while parked in garage with radio off so volume was too loud. I turned down volume and finally got system to respond to voice navigation commands. I turned off after routing to my work. It resumed routing this am and volume was off. I turned on radio and radio volume was fine but nav volume was very very soft. I could not find a way to increase volume.

Another thing that I wonder about is nav system will frequently show right turn in window dislay but voice will say turn left.

Any one have similar issues?

I have a 2008 MKX. You can increase the volume of the nav by turning it uo when the voice is speaking. It should stay where you set it, but if your radio is not turned up when you set it it will seem really low because the radio would drown it out.
In other words, turn the radio volume to normal listening level. Turn on nav and when the girl talks turn the volume up to a good level for you. It should stay that way. Hope this helps!