The D1/D2 wont give you text-to-speech like the Z1 does, but it does give you voice guidance. It will announce names of major highways/freeways/roadways, and exit numbers on those major roads.
Otherwise you will hear such guidance as:
"In seven-tenths of a mile turn left" (and in my experience, when you come right up before the turn it will say "Right turn ahead").
"Make a slight left onto the freeway entrance".
"Your destination is ahead on the right"
"You have arrived at your destination"
"Take the third exit of the roundabout"
I have a few major highways here in NYC, where it will actually tell me things such as:
"Make a slight right turn onto Exit S 1 East, onto I-495 East".
Also I have XM Navtraffic activated, and just this morning it helped me out of alot of traffic during the bad weather, telling me:
"In about 5 miles, there is slow traffic ahead" (and the screen would prompt me if I wanted to reroute or not).
My opinion, the Z1 is an amazing machine, but unless you are going to fully utilize all the features, it doesnt warrant paying all the extra money just for text-to-speech. The AVIC-D1/D2/N1/N2/N3 machines are all fantastic!