Whats the difference between the WinCE unit and the Android unit besides the software?
see the android thread or the FAQ on my website.
Does android use the GPS signal or WiFi to navigate?
Answered above by MaximumWalrus
Is there any way we can connect a USB device to Android side of the system for a 3G Wireless router or something?
I suppose it is possible but I only endorse the wifi route....too many compatibility issues for me to deal with going the usb3G route...
I usually use the USB function of the unit to play all my music. It loads up instatly on the V3 unit. Is there a delay for a 8GB USB Stick on these newer units? If so how long is the boot time?
Havent timed it but not long.....It can be seen in the video in the first post.
When the reverse cam is on, on the V3, music shuts off.. Does it do this on the newer units like the D99?
Can we download apps to Android without using a WiFi Connection? Lets say using a USB stick...
Yes, you can put the app apk on a usb or sd card and use the android app installer.
You mentioned the Android system has its own sound settings for its apps. Does the Navigation app turn down the volume of the music while giving directions?
Yes, but it depends on the app, works the same way as a phone or tablet, its probably going to work smoother if you are using the android music player as the nav and music programs are programmed to interact well in most cases.
Last but not least, v3 users had no control on the midrange, subwoofer levels and such? Is this still present on the newer units?
No midrange, but it does have a sub level control.