We're about to make that switch ourselves. Found out Comcast (southern US) offered it way cheaper (like, 70% cheaper lol) than stand-alone VOIP companies like RingCentral, Jive, etc. Don't have any experience with Amazon or Microsoft's offerings. Comcast's deal included bringing in a separate data line just for VOIP so we didn't have to worry about how it'd work on or interfere with our existing connection which was a big bonus. Amazon/Microsoft would need to use whatever internet you've currently got so make sure it's got good upload bandwidth. Might be worth checking to see if your ISP offers anything just because they can sweeten the deal in those ways.
Our contract has a 60-day back-out period if we need it and I think any problems would be obvious by then. If the people you're looking at offer that too, I'd say go for it.