Got the new Chromecast today and I have to say I much prefer the Android TV experience on my Nvidia Shield TV. The Google TV interface is slick and pretty though and I do really like the way they implemented the live panel with YouTube TV. I just don't like how my YouTube recommendations are buried now and I can't move them up to be more prominent on the For You page. If they just made the For You page more customizable like the home screen on Android TV I think I would be happy. Oh and it's borderline user-hostile now how hard they make it to uninstall an app.
I've been told AndroidTV/GoogleTV devs take a look at this subreddit from time to time, I hope they take into account your personal experience.