This is a well done feature. More than a naive list of the three most recently used apps, the sidebar reserves space for three specific purposes; one spot for maps, one for music / podcasts apps, and one for phone calls / messages. These categories map to the most common actions people want to do in a car — hands free chat, getting directions and playing some music. Subtle animations complement the behaviour and signpost state changes with smooth motion.
In iOS 10.3 beta 1, the time was squished down right next to the home button making the whole interface feel cramped. In beta 2, the time is centred in the available gap between the elements which gives it room to breathe. Much better.
On the CarPlay home screen, it does look messy as so many of the apps are duplicated as sidebar icons. I would hide the quick launch tray on the home screen and show the car manufacturer’s app in the top left corner instead.