Well unless you comparing full frame cameras (very expensive) then Canon's 1.6 crop compare to 2x does not get you much more dof for a given focal lengh, about half a stop and most of the med Oly lenses barring the kit lenses are a stop faster.
The grass is always greener on the other side, I changed from Canon to Olympus and have never regreted it, some people think changing cameras is going to get them better pics then end up dissapointed.