Well since you ask..
1, System-wide ad-blocking.. Yes browsers these days come with ad-blocking support. But have you been able to get rid of the stubborn ads that pop up in other apps. I know ads support the developer. But sometimes, they overdo it.
2, Substratum theming support (without Andromeda).. The Vivo's themes are garbage. Substratum could open up a world of opportunities.
3, Uninstalling junk system apps. Yes there is a method by which we can "uninstall" without root. But that's not a proper uninstall cuz the app is still in the phone and simply gets disabled for the user.
4. Making build.prop changes to add subtle tweaks that could improve usability in areas where the phone maker doesn't give a damn.
5. ViperFX..
So on.. And so forth.. Yes we can live without these things. But having them is definitely an improvement in smartphone usage... Especially with a beautiful beast like the Nex.
Cheers