I haven't used the Maps app that much since I got my Droid. I didn't have a problem the few times I tried it until this past weekend. It worked for one location near Cleveland, OH by correctly using the address of the place i found on the web and then navigating us to it using the Maps app.
The next attempt, i did the same thing, used the browswer to find a CVS and then clicked get directions and selected Maps when prompted. The written directions were correct, but once I clicked 'navigate' and the navigation began, it wanted us to drive like 2 miles past the destination, turn onto a different road, and then back onto the road were on. And no, it didn't have us go back to right place once back on the right road either.
Now, I saw the CVS once when we turned on the road, but it was like in a tiny little shopping center and looked more like a mom&pop pharmacy, so the others in the car didn't think it was the right place, and wanted to follow the navigation. Of course I "back out" of the navigation and look at the written directions again, which do indeed say the CVS was the one we just drove past, and when I clicked navigate, sure enough it wanted us to keep driving. Needless to say after riding the 1.5 miles down the road, the driver turned around and went back and that hole in the wall CVS was indeed the real cvs once you got inside.
I just thought it was so weird that the written directions were right, but the 'navigation' was not. I would think that the navigation would just be using those same written directions.