In all of these discussions on HN, the only ones bringing up "worries" about Cortana features have been people defending Windows 10 (and now Windows 8 and 7) data collection. It's easy to disable and, if you choose not to use it, it won't collect data anyways. The same can't be said of telemetry.
> Which tells them when you launch a Windows 10 "app" and some basic computer information
Actually it's not clear what else is being collected, because Microsoft won't disclose what's being collected. Is there evidence that only data about usage of Windows store apps is being collected?
> But even without that setting/ability the apps themselves could conduct the same reporting
Which would be needed to take into account when deciding on if that app should be used. Just to be clear, that means the application I choose to run might be collecting analytics, but my OS is also collecting analytics on the applications I'm choosing to run because it thinks it should.
> Nobody can actually point to exactly what specific information Microsoft is even taking
Yes, because Microsoft won't tell anyone what it's collecting!
> and have even less data yet still to back up any claims
As a baseline, you yourself talked about how we know they're collecting information about application usage. That right there is undesirable behavior for many that we have plenty of evidence for.