Had this combo on order for sometime but missed out on the first two shipments.
Initial impressions that it is quality built, compact and fits/balances nicely on the E-M1 with grip.
Also like the retractable lens hood and internal focusing so no external barrel extension.
Still playing around with settings but AF appears very responsive and accurate. Nice to able to shoot at f2.8 and f4.0 for a change.
Bokeh appears nicer then my 50-200mm SWD and IQ appears to be slightly better, but that is subjective at this stage.
Of course it doesn't have the reach of the longer telephotos so not ideal for birding. But will be real handy closeups such as shooting bugs, insects and butterflys.
Based on what this lens can deliver the 300mm f4 should be a very nice birding option.
A few test shots.