I would jump at this if the VoiceMail was deleted after being converted to SMS. Now I still have to access voicemail from time to time and clear the inbox. Too much effort.
I currently use their VoiceMail to Email facility which is great as I live at my computer, so an email is so much easier. But also, does not delete the voicemail so I still have to call 121 and clear which is a pain.