Mouse and keyboard isn't bad, I could even say it's almost good. It looks like it would be really good on a tablet but I haven't had a chance to try that out as I don't own any tablet hardware. I would say the place were windows 8 fails the most is on older laptops. It's painful to use with a track pad because it sucks having to mouse around so much.
The only other major complain i have is that the two different interfaces have a very different look and feel. It's jarring when it flips back and fourth.
When it comes down to it though, I can still do everything i did in windows 7. I just have a full screen start menu. If i use windows key and then just start typing what i want to run it's just as efficient. Metro Apps aren't that great on a traditional computer but i wouldn't be upset having them on something like the Surface or a convertible tablet.