I switched to the Olympus system (from Canon) one year ago and I'm very happy with it. The reason for this change is that i was looking for a system with great lenses in a compact package. I don't expect to make photos with the best tools available but to be able to carry these tools with me. Putting out the mirror from the DSLR is what I was waiting for:

1) Extremely small camera & lenses
2) Extremely light camera & lenses
3) Good photos' quality and complete functionality
4) Silent
5) Predisposed for quality lenses (wideangle and available-light)

We have to consider also other benefits:

a) Movies
b) Extremely rapid burst (30 FPS???)
c) Compatible with Canon e Leica M lenses (via adaptors)

I don't expect the new mFT bodies to be as good as the actual ones, but they will be really usefull. Maybe we won't see them on the football fields, but likely in a lot of common place (restaurants, offices, streets, ...) owned by amateurs loving to make serious photos.
I'm sure that the Nikon D3 is a great camera but I've never seen someone taking street-photos with it...

Thanks to Olympus and Panasonic!

(One note for Olympus: that was a great idea but I'm still waiting for a 25mm F/1,0 FT, don't forget it!!!)