Olympus Pen EP1 here. Hardly ever touch my Nikon DSLR. love it! Avoid the plastic shell EP-L if you want full metal case. I bet the internals are very similar though. Mine has survives two years of riding in a Camelbak (protected by small Lowepro case). Next investment is the new Olympus fast prime lense.
Mirror less is definitely the future for serious amateurs/semi pro.