I used OM1n's years ago when working as a pro. Couple of points, flash sync. speed not high enough for realistic "fill in" flash in daylight. Motordrive cover on base had a habit of "dropping off", best to cover with tape if not using a drive.

I recall some OM2's & OM4's suffered "battery drain", believe problem cured with later models. Great for carrying around, lenses excellent in the main. Unfortunately, Olympus (at least in the UK) don't seem interested in servicing them. Spares could be a problem.