This story from eWeek covers the topic of the pain that companies feel from their Exchange environments as well as some alternatives available to address that pain.  This story is consistent with what we see and hear across corporate messaging environments.  Companies are needing Exchange to do things above and beyond its original intent from being a file management system/document repository to e-discovery activities.  Unifying voice together with email all through Exchange for "unified communications" will make it even more mission critical as well as intensify much of this pain.  If you think your business comes to a halt when email goes down, just wait until it takes your voice system down with it.