We have a customer who has shot his OM-D side by side against his Canon 5DmkII and there is no difference in quality when printed out to 800mm sq, only differnce he found was the Oly was less than half the price of the Canon set up & a 1/4 of the weight, he is no longer buying Canon gear.
By the way all Canon users such as myself, Canon have discontinued all accessories for some of there camera bodies that have only just been finished & are still available new at some stores.
Batteries for the 1DS mkII for instance & WI FI for the 5dMKII we are very very dissapointed at this & it does make me wonder if I should dump them myself ?? They are not interested in photographers at all long term only box shifting from now on.