Extremely sharp, at any aperture (limited by diffraction), corner-to-corner!
Close focusing (3 metres) for a reproduction ratio of 1:7.
Internal focusing via a smooth rotating cam.
Nine diaphragm blades result in smooth bokeh and 18-point sun stars.
Outstanding build quality and precision, and resulting fit-and-finish.
Integrated lens hood.
The matched Olympus 1.4X-A tele-extender affects the image quality minimally, resulting in a super-sharp 500mm ƒ/4 lens!
Big and heavy, but any lens of this reach and aperture will be big and heavy.
Flourite coating on front element is soft and scratches easily.
No way to put a protection filter on the front.
Somewhat rare and expensive, although not as much as the 250mm ƒ/2 little-sister lens.
As a classic legacy film lens, it is manual focus only.
This is simply an awesome, classic lens!
It is especially useful for wildlife, motor sports, even macro. But with moving subjects, you have to use old-school manual focus techniques, such as pre-focus on a spot that the subject moves into.
It is still useful on modern mirrorless cameras via a simple adapter, but becomes even more awesome with the Metabones Speedbooster Ultra, which gives you a 250mm ƒ/2 lens for a fraction of the cost of the ultra-rare OM Zuiko 250mm ƒ/2.