These days, some may argue that the 8" tablet is the "perfect" size. It fits easily into a white coat pocket if you're a medical student or doctor. You can usually hold it in one hand. It's fairly light. If you own an iPad mini, you're probably using that more than your regular iPad because it's smaller, but not too small.
We can expect to see some Windows 8 tablets on 8" form factors soon. The Iconia W3 Windows 8 tablet from Acer might be one of the first ones to hit the market. This is an 8.1" tablet that will run Windows 8 Pro on an Atom processor. The screen resolution is 1,280 x 768 (or maybe 1,280 x 800?) and you can expect all-day battery life at approximately 8 hrs.
How many 8" tablets running Windows 8 will we see this summer?