I had an 80$ logitech keyboard (the illuminating short-stroke like a notebook variety), and when it began to deteriorate I swapped it with a 10$ Walmart special that was a slightly curved Microsoft one. I had been playing around on this typing speed site and was surprised to find that on the 5th attempt I had beaten my previous record with this new keyboard.

If I had a variety of keyboards at my disposable I think it would be an interesting exercise to test them in this fashion.