I had one for a while and whilst I didn’t much care for the video compared with my full-frame Lumix at the time (S1H), I did like the stills files, but most of all, the form factor; the weight, ergos, build and sheer ‘rightness in the hand’ of the thing.
Also the lenses, both the fast primes and the zooms.
If I was ever going to do 4/3rds, it would be the OM-1 without having to think about it.