The Sony Vaio TZ keyboard is certainly a beautiful piece of keyboard. I always thought that such flat keyboards are not fast to type with, but this article might prove me wrong. I'd like to give such a keyboard a try in the near future. Apple also has some keyboards that are similar to this one.
It may be a pleasure to type on an IBM Model M, but it certainly looks very cheap. Its mechanics is interesting, but I don't know any museums around here to have one to try. Maybe I'll look up some auction sites.
I've always loved the mechanics of laptop keyboards, and there are some fake-laptop keyboards for the PC, but none of them mimics the mechanics of the real laptop keyboards. Fortunately, it seems that it's possible to buy laptop keyboards and mod them to connect to other machines.
According to the little research that I've done it seems that the pitch distance (distance between keys) is 18 mm in case of PC keyboards and it's around 17 mm in case of laptop keyboards. The stroke distance (distance a key moves when pressed) is about 4 mm in case of PC keyboards and it's about 2 mm in case of laptop keyboards.
I think tactile feedback is a strong attribute of a typewriter's keyboard which is mostly a combination of stroke distance and the used mechanics. Short stroke distance may result in insufficient tactile feedback and long stroke distance may be uncomforable and unproductive because there is too much path to take for your fingers to press a key.
Unfortunately nobody has published any extensive tests about people's typing speed when using specific keyboards, so I'll try to do such a research by myself. I'm afraid it's gonna cost me much time and money, but I'm sure it's gonna worth my efforts. I'm thinking of creating a frontend for people to populate such a database. Researching this would be a cool project.