10 (and IIRC 8?) felt incredibly slow on my gaming PC until I switched to an SSD for the OS disk. I think it hits disk way, way more often than 7, which makes it feel slower. Even on an SSD it doesn't really seem any better than 7 did on spinning rust (programs load faster, of course, but you can't really credit the OS for that—the OS interface itself, and OS utilities, don't seem faster). This was true even with Cortana and all that junk totally disabled.