I would give it a few more days. Our experiences are different but then so are the uses.
I have not tried hangouts yet. Will do today if it's out there. I only use hangouts to get text messages from my daughter on her wifi only iPad Mini. Messenger wise, I really liked Textra for my Note 3 but am willing to go back to stock for the sake of using my Gear S.
GPS wise, the Here Now app is in Beta and I read on XDA that it will likely open up all avenues of travel means when it goes live. Honestly, I'm not sure I'd use it in my car anyway. I really like using my phone and have it mounted on my dash perfectly. It also helps that all our cars have built in GPS too.
Music wise my gripe isn't so much streaming it's the sound quality. I'm spoiled by PowerAmp and it's amazing EQ and sound quality.
My guess is as these devices evolve more and more will come to them. Especially given they are stand alone units. The app developers need time to get things going. I mean this is the first of the connected devices and one with a larger screen.
Another Update that I'm testing is I actually tured off the GPS Feature to see what impact it has on battery life. If it's like my Note 3, I bet it's huge. I only need it when I'm out and about and looking for something anyway. Otherwise, like my phone, I don't need it on all the time. Stay tuned.