I like Windows 7, but I also turn off all the gidgets, wizmos, and wadgets. I square the corners of my windows (hate rounded edges), but then I pretty much try to forget about the interface tweaks, and minimize any fancy graphics.
Windows 7 is more stable than XP. I skipped Vista, and I'm pretty brutal with killing background processes and daemons. That said, I'm comfortable at this stage with the notion that Windows 7 is the more stable OS, finally, as compared to XP.
But my big complaint with 7, is that they try to make it "easy" to use for even the most imbecilic technophobic nincompoop. They reorganize menus, remove options, take away granular control over settings, and try to make the whole OS experience more like browsing a website by the Food Network. This really pisses me off, as someone who has spent the better part of my life (since Win 3) becoming proficient with the OS. Any reasonably competent human being should be able to comprehend the basics of Windows. The fact that some adults are apparently stumped by an interface that 3rd graders can master, is no reason to dumb down the OS for the rest of us.
I fear that this Windows 8 GUI is an attempt to take this paradigm even further. Instead of forcing old lazy Luddites to use some neurons, they're forcing everyone else to waste theirs.