S voice is quirky as I expected, doesn't hear things like I said it, but thats to be expected. I don't know if this counts as a bug per se, I know it's not a bug, but certain exchange accounts conflict with the SMS Sync feature of the phone when it is turned on and you have Sync SMS checked when setting up Exchange mailboxes.
This is new to me as I have never had the option, but by accepting the defaults and leaving Sync SMS checked, my work's exchange server was disabling my active sync to my phone forcing me to go and re-enable it on my exchange account.
Nothing just unchecking Sync SMS wouldn't solve, but still, it took me a bit to realize it because I had never had a phone with that option.
Also, when the Wifi voice option is selected, it seems the cell radio is shut off and you cannot receive calls and/or send/receive texts. I had to disable the wifi calling to get this to restore connectivity to my provider, again, not sure if working as intended but figured I'd throw it out there.