Over on the Beeb they are saying that there's talk of making Windows 10 a subscription based OS. If this is true I assume there will still be a purchase up front option as well for a ludicrous amount of money. Going subscription only would be the thing that finally pushes me over to full time Linux use, to be honest I'd be there already if it was possible to run MS SQL under Linux.
Over all what I've seen of W10 looks ok. I use W8 at the moment and to be fair once I got over the whole "OMG what's happened" of the initial install it's much like using W7. The whole Metro thing is still a PITA but I hardy ever find I need to go in there. I managed to transition my parents over to W8 with no problems so it can't be that bad :-)