One of the really important things for me with the system is that it has a good screen, if its a cheap chinese screen that is useless in the sun I wouldn't buy it. 
  
If i could have android on the screen the same as my phone I would be a happy man.  I know how to use it already, its nice, clean and useable.  Can i connect my HTC to it to utilise the internet connection on the phone allowing it interweb access? 
  
My list of top four essential things I want as a customer 
  
-Good screen that i can see in the sun, has multitouch and looks high quality (think ipad) also fits like it was an OEM unit 
-The system is reliable, cant be crashing all the time 
-system is fast, reacts to touch input in good time and processes map routes etc quickly (think tom tom) 
-It is easy to use, i dont want to faff about a million menus while driving (again think tom tom) 
  
  
Bonuses i'd like 
-connectivity to internet 
-cool looking nav software 
-Plays movies and music 
-turns on when the car is turned on (can be changed in a menu)