Listen I think if you are content with your current setup (be it 8.4 or smaller) then stick with it. I am SURE there are going to be issues with a unit like this. Not to mention if something goes haywire with the climate controls or something else "controlled by the radio" chances are you'll need to swap back to the original radio before a ram dealer would even seriously look at the vehicle for an issue. Example; on my jeep cherokee that I had before my truck suddenly the AC stopped working, wasn't blowing cold air. Took it into my dealer and after a full day they came back with "oh, the connector on the controls came loose, we pushed it back in and you're all set now" Imagine if one of the connection on this back of this unit become loose... yeah issues galore.
This isn't a "main stream" unit, if it was it'd probably be closer to $1,000 to 1,500 for the features it boasts.