Before Primo... there was IGO 8. It was great actually. With a dimka skin, super efficient even on crappy winCE devices, I don't count the android version... its NOT classic igo8 but some amigo +primo abortion

Primo itself... lets see
*new skins were a shock.. but 100% required for usability
*GL support broken
*several key press and confirmations to avoid roads
*tells me CO2 emissions and not $$ when planning route
*routing 10% smarter than myway
*extra convenience things like parking around destination, show certain POIs, etc.
-Still needs MAAANY sys.txt mods to make it a navigator and not some phone toy

Nextgen
*GL + DPI settings
*much better/more labels visible on roads
*less cluttered menu
*avoid roads easily now
*no quick menu so needs more UX addons
*less settings for sys.txt to get useable
*more and more "online" features..
ok I get it.. but I can use google maps for free if I need all of that and want my gps coordinates sent to a 3rd party

so long story short the UI/engine is better on nextgen. A properly cracked version for content and maybe it will be my new igo8