SMB Phone System Buyers Guide by Focus Research
I noticed that M5 was featured as one of the hosted PBX providers in this phone system buyer's guide by Focus Research. This guide is a pretty nice overview for business users in the research stages of getting a phone system. Much of the advice is obvious- but still quite helpful to reiterate the kinds of things you should be going through as you go through the buying process.
What I found missing is just a bit more detail. It would have been great if the guide went into a comparison of different vendors- I think M5 is a perfect fit for users they call "Fast Featurists" who want to take advantage of advanced features and integration.