I don't find Win8 to be buggy or unstable BUT if someone does, it's going to be Drivers issues. And poorly-written drivers are, historically, because Microsoft gave out wrong instructions. Driver Programmers can certainly write idiotic code but most of the time, they're only following Microsoft's designs. And then Microsoft changes them frequently, and it's a hoops-of-fire leaping contest to see if Drivers can be re-written in time for devices.
Win8 lacks User Customizations, though. There are themes galore, but individual element customizations are hidden away by the UI, disallowed by Ballmer & Associates. You better learn to love THEIR schemes and limitations because YOUR usability choices are all but gone.
Win8 gets a lot of positive praise when 3rd-party add-on's reduce it back to Win7-or-earlier UI abilities, but with the 8.1 coding exercises on display, it appears at least some of those are castrated. And Win9 might take those cutbacks and usability reductions even further.
Win8 looks great for shopping and watching. Is that what you do all the time? Or if you need a lot of controllers - or foresee the need for controllers and other hardware to match software, then raise your antenna and think, "So - I need drivers, eh? Gee - are drivers better on older, tried-and-true platforms, or the latest bleeding edge stuff?"