We have just switched from a BT analog business line to digital Voice Cloud Express and I thought you might like to know our experiences. I set up the hardware before the switch because I was due to be out of office for a week. Following the switch we had to disconnect analog phones and reboot the Smart Hub 2 plus Yealink W73P base station.
I found the marketing blurb Halo confusing because I could not find correct help online. I did not realise the Voice Cloud app was not just a mirror of the online portal but caused my mobile to ring in synchronisation with the landline which was embarrassing when in a customer meeting on site. When I did realise I swapped the app over to our administrator back in the office and set voicemail forward to my email.
We found as we tried new functionality was intermittent at the start until used a few times, for example answering landline on a mobile and we could hear caller but for them volume was incredibly low. Then after a few tries the problem fixed itself. I recall a BT comment that it takes a few days for the copper cables and exchange to adjust to the new signal.