This was my main camera since purchasing it in 1987 following the theft of my OM2s Program and then much deliberation on the Nikon vs. Olympus argument. At the time, most Japanese cameras were very reasonable, but the Nikon lenses were significantly more expensive than were the Olympus versions of those same focal lengths. But beyond that, I was very enamored with the idea of the multi-spot metering, which Olympus had pioneered. It is an essential feature for achieving exact exposures under less-than-ideal lighting conditions. I'm a big fan of back-lit or "rim lit" lighting, and this camera makes it so easy to do and get a great exposure. Today, of course, the "matrix metering" and other ways of automating this process are included in most pro and semi-pro cameras.
Also unlike Nikon, this camera was very compact and the ergonomics were wonderful. It was easy to use right out of the box, and remained so for the 20 years I owned it. Other than one trip to Olympus for a cleaning and calibration, this camera never needed service at all and remained accurate in terms of exposure.
In terms of lenses, I tended to keep things quite simple, starting out with the Zuiko 50mm f/1.4 standard lens. For whatever reason, at the time it seemed (and perhaps it is still so) that this was the focal length and maximum aperture that everyone needed to have. But after having owned this lens for two decades, I must say that I was never terribly fond of it. The optical performance, in my opinion, was good, but not great. Barrel distortion was noticeable in any images where straight lines are near the edge of the frame. The color rendition seemed a bit off, perhaps towards yellow. And the contrast seemed slightly soft, giving the overall effect of images without "snap". Thus, I did not use this lens very much during the time I owned it.
The lens I used most often with this camera is the Zuiko 28mm f/2.8 which proved to be a very versatile performer, with a reasonably fast maximum aperture and very low distortion. For many years when traveling, I took only the OM4 body and this lens.
In terms of "love" for a lens, though, nothing in the Zuiko line compares to the 85mm f/2 short telephoto. For semi-tight portraits, this lens was wonderful. Although it was not distortion free when compared to lenses such as the Zeiss 90mm f/2.8 G, the result was still wonderful. The selective focus ability due the wide maximum apterture, the sharpness, and the color balance put this lens in a much higher league than the original price would indicate.
My last addition to the Zuiko line was also used quite a bit: the wonderful 50mm f/3.5 Macro lens. It was truly an outstanding optic and a bargain on the used market. I picked up a set of Vivitar extension tubes to accompany this lens, and the results overall were truly excellent.