re: Windows 8 Won't Be Saved By Keyboards
Also, separate point about the laptop usage.
Forrester samples knowledge workers, who are more securely tethered to keyboards than most people. Introducing a tablet only has to reduce laptop use if one assumes that overall computing activity is static.
I, for example, have both tablets (with keyboards) and computers in my household. A few years ago, I had only computers. Today, I probably spend 20% of my time on a tablet and 80% of my time on a computer-- so in percentage terms, my PC usage has declined. However, I type a ton more today than I did a few years ago, which means I spend more time than ever before looking at a laptop. I also spend more time at my desktop working on other things that tablets aren't suited for, such as photo and video projects. My overall time spent at computers has increased by a huge margin. So in that sense, my PC use actually increased DESPITE the introduction of a tablet.
I might not represent a typical case, and I think you're probably right that, on the whole, most people spend less time on their PCs because they now have tablets.
But you can see why only 35% of knowledge workers would perceive that they're using their laptops or PCs any less, or that their laptops or PCs are any less essential. The number of them who do substantial typing on a tablet is predictably confined.