I took P20 and Oly 75-300ii with the E-M1.2 to the 7-mile stroll.
Both can be slow if the camera has to go through the entire range but P20 is positively unusable unless you put it to single point AF. Which is more than fine for me.
Therefore Olympus user definitely might want to lean towards the O20Pro if they feel the need.
For comparison, on every Panasonic body the lens does a bit more alright and you can use f.ex full field autofocus without strong problems. Of course it isn't bottled lightning there either. Very few of my primes can match the focus speeds of the P12-32 and P35-100. Maybe the P42.5 is the only one that can keep up. The others feel slower in comparison.
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I tested C-AF and high framerate bursts (e-shutter) on the E-M1.2 and it was doing very alright. Heat haze, shutter speeds too slow for aircraft, and lens' poor performance at its 300mm end have to be taken into account but for example using a 5-point crosshair pattern did result in plenty of satisfactory series of photographs. I believe the keeper rate would have been top notch (> 90%) if I had bumped up the ISO to allow 1/1000 shutter speeds. I'm counting this one series of 44 shots, all in focus. Not bad.
Certainly it is a power house like the 2016 reviews and sales pitch told us, and is top performer of my camera stable. The ever-able salesmen just got the world convinced that you must have the perfect continuous TRACKING autofocus in your camera before you can call yourself a man.