Even with SM, we test it before we deploy it, they release on Thursday, we spend Thursday evening and most of Friday testing items, but we can only go so far as our clients have a much wider test base than we can do internally. Some issues do not show up until we've installed on our production system as well. Like this last update fixed an issue were some emails were getting stuck in queue due to an unhandled exception. Fixed that, now we have broken IMAP for Thunderbird clients it seems. So we go back and forth with SM fixing and breaking things.