A famous mechanical keyboard site claims that:
Many mechanical keyboard fans rave at the loud, clicky sound they produce when using one of these keyboards. As mentioned above, the mechanical switches that make this loud noise are what’s ensuring the computer registers every single keystroke, therefore improving typing accuracy.
A few writers and programmers have tested their typing speed and accuracy with mechanical keyboards, and the results are impressive. One writer found that he was able to put in 91 words per minute at 100% accuracy, which meant he could type a whopping 900 additional words per hour with less errors. Imagine how much more your employees could accomplish with this ability.
(source)
They claim this is based on a few "impressive" results and provide one anecdote. Are there any valid studies on the matter?