The only con I can think of (and have actually encountered) is that when using 1-series bodies and lenses with their own L-plates (such as the 70-200), the bottom of the 1-series body can block the lever when attempting to open or shut the lever. This would only happen if positioning the lever on the "left side" -- i.e., the side on which the IS on/off, AF/MF, etc. switches are for the lens. I prefer to use the lever on the left side, because I often hold the camera in my right hand and operate the lever with my left hand. You can minimize the issue by positioning the lens a little farther back, so that the front part of the lens plate sits in the clamp; this offers a bit more clearance. There are other workarounds and ways to minimize this issue.