Well, my understanding is most of the telemetry data concerns application launches and crashes... so they, in effect know which software you are installing, and how it is doing overall. Not to mention other potential tracking information (software piracy trends). This allows them to intercede and know what areas to invest in internally.
The pro and enterprise versions allow you to disable pretty much all of this. The Home version is less able. A lot of the additional data is leaked by using cortana for searches.
That said, I'm not too paranoid about it, but I do understand why others may well be. Also, MS has been doing everything it can, including relatively great pricing to move SMBs to their hosted solutions for AD and Office365 packages. Which I can see as appealing for MS and SMBs. The more recent workspace/scheduling applications added to o365 show this direction, and integrating with LinkedIn cements this a little bit.
Who knows how it will work out in the end... I've been specifically pushing Docker Cloud simply because it can target multiple cloud systems for deploy, instead of the walling in from AWS/GC/Azure in terms of a lot of their own Docker tooling support. In the end, you're paying someone. How much you pay and what you get out of it will vary. But you are paying.