I just bought a 2016 Accord Touring and I expected Android Auto (AA) would be better (e.g. more useful) than I'm finding it so far.
The built-in (new to 2016) Garmin navigation seems superior to Google Maps via AA. (I've always felt that Garmin was the most superior navigation platform, but Google Maps has been a close second as a fallback, or when it wasn't worth the effort to pull the Garmin out of storage and mount it on the windshield.)
The new built-in Garmin navigation has most of the functionality of a high-end Garmin PND (traffic, trip planning routes, etc.). The Google Maps navigation in AA does not let you search on route, and doesn't let you save a trip with specific waypoints (yes, Google just re-added "search on route" back to Maps, but I can't see any way to access it through AA -- and this has me wondering what the actual relationship between Google Maps on the phone and AA really is). And, for some reason the Google Maps UI on AA doesn't seem as "slick" or appealing as Google Maps running directly on a phone.
So, of the three features AA brings to the table (Navigation, Phone, Audio). This one goes to the built-in Garmin.
For the Phone feature, I see little, if any advantage to use AA. Without AA the phone integration with the car still works fine over bluetooth. Honda's infotainment UI presents the phonebook over bluetooth just as well as Google does, and the phone over bluetooth actually works better. For some reason the audio in AA is VERY LOW for the phone (and also for navigation prompts). I've tried everything and can't get the call volume and navigation volume at suitable levels -- so AA is actually NOT preferred for phone use (and, for the other reasons previously mentioned, not for maps use either).
So what's left? Just audio/music. I'm not much of a music nut, so this category has a smaller weight with me. AA has the advantage of being configurable to use a compatible audio app on your phone. But, HondaLink over bluetooth has AHA which, while not quite as powerful as Tunein Pro, still has a lot of the same content. And, it's not that hard to play audio from the phone through Bluetooth or Aux input without all the restrictions imposed by AA. So I don't see music/audio through AA as much of a benefit.
So, all told, it seems AA needs a lot of improvement to be a substantial player -- particularly with navigation features, and phone and navigation audio. I also suspect Google will have to eventually be less restrictive with the Maps/navigation portion and not limit it to just Google Maps, or they'll run into antitrust / anti-competitive issues.