I shot Olympus for a long long time... The user interface on the Oly's beat Nikon and the Rebels hands down... but was inferior to the pro level canons... I needed the camera system to be very portable and the extra reach of 4/3 was a bonus. Sensors were equivalent in IQ to Canon and Nikon APS-C and the selection of quality lenses was growing quickly. Oly 4/3 was the right choice for me.
Then came micro four-thirds..... All of the developement went into micro 4/3 cameras and lenses. I HATED the user interface, the lenses were all low quality and the cameras/bodies were not sealed, and the ergonomics, at least for me, sucked. 4/3 users were left out in the cold.
We Oly users waited patiently for the next "pro" body..... and the E-5 came out. I had one pre-ordered and when I went into the store to pick it up I was so dissapointed in it (the PEN's took better pictures) that I walked out of the store with a 60D.
I picked the 60D because:
1) reasonable price
2) reasonable quality pictures... way better iq than 4/3 cameras of the time
3) great ergonomics / user interface (love the tilt/swivel screen)
4) Lens selection (still nothing long availiable for 4/3 or micro 4/3)
5) Magic lantern
6) Semi-sealed body... would have prefered fully sealed, but way better than no sealing
7) size was good for backpacking
APS-C for longer reach without getting lenses too big to carry up mountains
9) second party lenses and accessories
Since I got it, the only thing that has changed is that the iq of the latest micro 4/3 cameras is slightly ahead of the current crop of APS-C cameras (still behind FF), but all the other shortcomings of micro 4/3 still remain... I'll keep shooting with it until a much better APS-C canon comes out, and ignore incremental upgrades.