1) How easy is one to use vs the other? If you're used to Google Maps on a phone, using it on Android Auto is very intuitive, maybe even easier since they've simplified it to remove distractions. I haven't used the built-in nav much, but it seems to work fine compared to others which are equally ugly, outdated, and clunky. One more thing, the built-in voice control is horrendous. My wife tried to tell it to call me and it started playing music. It is truly pathetic. Voice control on AA works as well as on the phone, which is pretty decent.
2) Are the AA connections easily made via bluetooth? Android Auto works over usb, though when you connect a phone for the first time it does also connect over bluetooth for phone functions. When you first connect, you need to make sure Android Auto is enabled in the car and the Android Auto app is installed on the phone. When you connect the projection icon on the screen will change to Android Auto. Tap it, Android Auto launches on the phone, and you'll have to tap through a few confirmations to give Android Auto access to your information and such. After that, just plug in and it works.
3) How much juice does this pull from your phone? Ehh, negative 2.5W. The Volt supplies your phone 500mA to charge, which is on the slow side, but with the screen off my phone charges fine.
4) Can you manipulate the "nav" display similarly with AA or the builtin system? AA has pinch to zoom while the built-in uses + and - buttons. Built-in is far less attractive and doesn't show traffic.
5) Are there any other irregular integration issues with the remainder of the system using AA vs the builtin system? So far so good, if I'm listening to the radio AA navigation still comes through no problem and I can access other screens with no issues while using AA. I like to set the driver's display behind the steering wheel to show audio information so no matter which source I'm using or screen the mylink system is on, I can always see song info and change tracks using the steering wheel up and down buttons.