I own a Nikon F as well. Yes, it has mirror slap but once you do mirror-lock-up, the shutter itself is one of the most stable in history. So shutter shock should be considered. It was Celestron, if i recall correctly, the ones who tested many SLRs in the early 70s and found that the Nikon F shutter was the most stable of all, and thus they were recommending it for astrophotography.
The contemporary Nikkormat FT2, for example, has much more shutter shock compared to the Nikon F; comparison using mirror-lock-up. I owned one as well.
Now, regarding the Nikon F, you can't compare it to the OM-1 since the Nikon F is a 1959 design, the OM-1 is a 1972 design. By 1972 the Canon F-1 already had an excellent anti-mirror shock device. Can't comment on the Nikon F2 since i haven't tested one, but i'd expect it to be similar in this regard.
All in all i don't find any "unique" feature to the OM-1 except compactness.
Regarding my "compactness is for wussies" claim, i do think that Olympus, Maitani and his OM-1 are responsible for something very wrong in lenses after 1972 -- compactness and lightness above performance. Particularly, Canon brought the "New FD" line which were lenses that were noticeably more compact and light (obviously to follow the trend set by Olympus). The result? In some cases inferior performance to the previous FD line, and in all cases, less ruggedness and quality of materials.