Even with it being free that's just not enough to get me and many many others to make use of it. There are lots of things that are free of monetary cost - that doesn't mean you're not paying for them in some manner.
Microsoft isn't giving Windows 10 away for the first year of release for free and not getting something out of the deal so it's costing end users whether they're cognizant of that fact or not.
I won't be willfully ignorant of what's going on, and I highly recommend nobody else be that way either.
It gets them closer to supporting one OS. The ultimate savings is dramatic and if they managed to get virtually all consumers to move, then, I suspect, it'd save them a lot of support costs. Note that my assumption (which may be invalid) is that businesses tend to have less diverse h/w. I know where I work, pretty much everything is a dell desktop or laptop and they're generally plain vanilla. Last company was the same thing (may have been a different brand, but it was from a big pc builder).
All of that ultimately benefits me the end user. Now will this work out? Ask me in 6 months. So far, I think it's fine, though I've heard that Threshold 2 had some issues at launch, which tells me they probably don't have enough diversity on the fast track program.