Having personally seen Tundrav8georgia's z1 unit in action and having used some of the features on it. It is a pretty fast system - already has your location the moment you click OK on the 2nd warning screen.
Also the neat thing about it is you can program the "GO TO" button to default to your home and you can use this to instantly compute a route to go home. Also its dead precise when you have it at 0.1 mile scale, I compared the accuracy of this unit to my laptop's GPS program and indeed, its smack on accurate enough to make your head spin.
It even has an indicator for which lane you should be in when you make turns (if you even have the voice guidance off, it'll show you). Very helpful when you're on a freeway and need to know what lane you should be in, in order to make an exit.
You will have to get the installer to wire it up in a way that you can flash your lights on start-up so the unit sees it as a signal to boot straight up instead of hanging at the copyright screen.
Also, sometimes I noticed the voice command unit slips up with his voice command requests, thinking it means he wants X when he really wants Y. You have to be a tad firm in your voice command and concise to get the unit to respond with the correct answer.
Thats pretty much my assessment of the unit for the time I've been with it.
Sanosuke!