For myself, it's really a matter of sticking with what works until there is a pressing need to change. Win7 is well-proven at this point and is still good for four more years. The fact that I've always rode the coattails of technology helps. My main system is a now-ancient Core 2 Quad. I've souped it up in the last year, and actually in process of making a couple more upgrades to it. It still does modestly well for games and just about anything else I might care to dabble in, but the fact is I'm running on hardware standards that predates Win7 itself. If I had the desire, to say nothing of the budget, to stay current on hardware, the need to upgrade would probably press on me more.
Even with the incentive of a free upgrade and a hassle-free rollback if I don't like it, I'm ok with eventually have to pony up for an upgrade when extended support ends. My experience with Win7 has been almost universally positive, and I'm not one to mess around with a good thing.