Overall, it's an amazing phone for the price, but we did have to work around one major issue. We could not move any apps to the 64GB microSD card that we purchased with the phone. The card was detected by the phone and looked just fine after formatting, but all attempts to move apps to the SD card using the System Manager -> App Manager -> App Move, failed with the message "Move [App Name] Failed, Insufficient Storage" Note that the SD card was otherwise working properly with apps like Google Play Music using the SD card for the music cache.
After lots of Googling, I found a link (can't locate it now) where it was suggested that this may be caused by a phone that struggles with more than 32GB of free space on the external SD card. Moving apps to the SD card would work fine for a 32GB card, but not for a (mostly empty) 64GB card. The solution was to fill up the SD card with some data to drop the available space under 32GB. I initially scoffed at this, but after finding no other solutions I figured it was worth a try. I shut off the phone, removed the back, removed the micro SD card, inserted it into an SD adapter, and plugged it into the home PC. I then copied 33GB of music into the ./Music folder and reinstalled the SD card into the phone. After booting back up, volia!, I was able to move all eligible apps to the SD card without issue (again used System Manager -> App Manager -> App Move).
Hopefully a future firmware/Android update will remedy this issue, but in the meantime, it's a pretty good workaround.
Two final notes:
1. You don't have to use music so any 32GB+ of data should solve the problem (photos, movies, etc.).
2. This phone has not been rooted. It's running the factory installed Android 4.4.2.