So far I've not found any bugs. It just does its job flawlessly.
It sounds crystal clear to the folk I have been on the phone to. Most disbelieve I am driving but then that could be the Golf being that quiet

Voice dialling is only available on the RNS as far as I know.
A2DP works but I rarely use it as it isn't as clear as the onboard music options. However the kids like to pair their phones to the unit and stream their music so they can choose what to listen to from the back.
Back to your unit not having a phone button, how do you access the phone functions if you have the VW bluetooth system as that is what the Fiscon unit works on!! Maybe worthwhile going to your local dealer and seeing how that system works.