It depends entirely on what I am typing on, and what I am doing. Accuracy is over 98% with all of the following.
With Alps, 60ish WPM, with heavy fatigue fairly quickly.
With Black Cherries, 90ish PWM, fatigue takes quite a bit longer.
On BS I can sustain about 110WPM. The problem with that is I get "In the Zone" so to speak. I'm fine when I am typing (and not thinking about it. If I have to think, IE, HTML structure, then I slow right down to about 20-40WPM, regardless of the board), but afterwards, the joints in my fingers know about it. I then have to retire to Cherries for a few days for them to calm down.
I am a very heavy typist, and consistently bottom out BS. If I manage to improve my technique and not bottom out, then I suspect that a heavy Cherry switch, such as the blacks, would be my fastest. The trouble with fast typing on an M is that it is extremely annoying to others around you, to the point I had to bring home my M today, and am taking the cherry into work tomorrow, as, the noise is just too much. The most common comment is that it sounds like "rapid fire machine gunning". This does not bother me in the slightest, as I have grown used to it over the years. Others however, cannot stand it.