I owned this lens for many years, and during this time I have come to realise that focal lengths longer than 135mm are something I rarely use.
I purchased it at a time when I was building my collection, thinking I needed something in this range. It was not long before I realised I only occasionally stray into long telephoto territory, so I often questioned why it should remain in my collection. I am sure there are photographers out there that would put it to good use if I were to part with it. The cost of this Zuiko has dropped significantly in recent years, even though it is used with some success as a 600mm lens on E-System cameras, with an adapter.
This is one heck of a lump of glass! Large and heavy, it is never used without some kind of support. It has an attachment which allows it to be screwed directly onto a tripod or monopod, taking any strain away from the lens mount. It takes larger, 72mm filters which can be expensive; however I only ever use a UV filter. The end element is large and probably expensive to replace (assuming one can be found) therefore the UV filter remained on the lens at all times. Like most OM Zuiko's, it is constructed with an all metal barrel which is undoubtedly where most of its weight lies. It is its weight, however, that instils confidence regarding durability, and I am sure it would provide a lifetime of use, if not abused.
At 181mm long and weighing in at just over a kilogram, I never really favoured this lens for overseas trips. I have been on the wrong end of airline check-ins regarding hand luggage weight restrictions on more than one occasion, thanks to this item. I am sure it would travel well as hold luggage, but never wanted to risk it. It is also a heavy piece of hardware to retain a permanent place in my camera bag, as a day out hiking with it, and a few other lenses gets onerous. So I guess that for me, the weight became one of its key limiting factors.
I used the 300mm focal length less and less during the last several years, and I recall it only being used once in the year before I parted company with it. In the past, I found it very suitable for landscapes and outdoor location type portraits and probably used it for the latter more than any other subject. The results are excellent, even wide open. Coupled with a 2 x or 1.4 teleconverter I am sure it would make a great wildlife optic. But for me, it became a sleeper and closet queen, emerging from my bag more for me to marvel at the engineering and build quality than put it into use. In retrospect, I think of it more as an expensive mistake made whilst hastily building my lens collection, so sold it to provide funds for other equipment.