This is going to sound fuddy duddy, but I'm not happy with most modern aftermarket radios.
Look at them compared to OE stuff and you will find the following:
Tiny buttons - tougher to see/work and all the same size/feel. Stock stuff is designed so they feel different and you don't have to look to see what you are doing.
Removable faceplates - Seems like more gismo and stuff to go wrong to me. It also does away with knobs in favor of the small buttons.
multifunction buttons - I don't like having to sort thru menus to select stuff while driving.

displays that are flashy but hard to read at a glance. This goes with the menus.

I have a couple car radios that I need to update. They will probably be replaced with OE radios, either stock or that have been refurbished/updated rather than an aftermarket head unit.
STOCK

AFTERMARKET