It has nothing to do w/ TeleAtlas. There are other map search engines out there that use TeleAtlas and are up to date. The problem is that Pioneer takes too long to put out updates...By the time you get them they are years old.
No, it's Tele Atlas. I just had the latest TOM TOM (Tele Atlas) for a test run and it had the same errors and omissions that I find in the Z3 software. Also the same poor routing. Google maps (Navteq) is the bench mark when it comes to evaluating GPS mapping and routing.
What happened to my Tom Tom? It went back and was replaced with a Garmin 770 which hopefully will do a good job in the rental car in Europe.
I've read however that Tele Atlas is better in Europe than it is in North America. Google Maps is excellent for Europe too so hopefully the Garmin will be as well. We'll see. 
That GPS magazine link by Passat is a great find for in depth info.