Re: We will tell them it's free - Muuhahahha
"This is more than a one-time upgrade: once a Windows device is upgraded to Windows 10, we will continue to keep it current for the supported lifetime of the device – at no cost."
The problem with this should be obvious if you look at web sites which have introduced tiered service or paywalls. They begin gimping the free service to encourage people to pay for the ungimped service. LinkedIn for example started off free and then started crippling search and email to get people to pay.
Or look at game consoles - if you want multiplayer or a smattering of other features like cloud save on your console then you have to pay a subscription.
It's easy to envisage Windows going the same way. Maybe an ad tile starts appearing in your metro. Maybe backup/restore, antivirus, cloud storage, remote desktop etc. become "premium" features. Maybe the ability to have more than 4 users becomes a premium feature. Petty restrictions, adverts and limitations could peppered through the experience and only lifted for a low, low monthly price. Maybe they sweeten the deal by promising streaming music, apps or unlimited storage or whatnot but through a combination of carrot and stick they want your money.
Now I doubt any of this would be tolerated in the enterprise world where I expect we'll see a "pro" Windows which is the same as always. But it may well be what MS have in store for consumers, particularly the free download and whatever surprise updates you get in perpetuity.
I hope to be proven wrong, but Microsoft isn't a charity and it's clear from their statements where they see their money coming from.