Very bad, at least in our case (small company). They reply mostly with templates. When one issue would have taken a bit more time to solve (Thunderbird IMAP issue with ONE of our user names) they simply stopped responding after a while.
AND: You can NOT go back to the free service, at least not easily! Talk about lock-in...
AND: You can NOT go back to the free service, at least not easily! Talk about lock-in...