It all depends. I travel a lot and suck at directions so mine helps me a lot and its a cool little unit

 

If purchased through them it will cost a fortune, a couple of members on this forum conducted some tests to see if these discs could be replicated with great success. I was able to get a hold of these. I can get the latest upgrades if anyone is interested.

 

I use garmin and IMHO highly recommend add-on Navis with suction cup just because it's easier to use elsewhere other than your Z.

 

stock looks better... but I think the features in my pioneer make it a more practical unit... The only thing thats not cool is that the screen is where the stock head unit is not where the OEM nav would be.

Too bad there isn't an easy system that fits into the stock compartment with touch screen... that would be perfect...