The adapter adds depth to the OM lenses, negating their small size. Sigh. With the superb Zuiko 21/2 (equivalent to 32mm on a 35mm "full frame" camera,) the combination is almost as large as the 18-55 zoom that came with my X-Pro.
My initial attempts with the 21/2 were ho-hum, but that has nothing to do with the lens. I was just learning. But with the 28/2.8 (equivalent to 42mm "normal",) combined with a little more skill, I seemed to find a sweet spot.
I missed focus (on the eyes) a bit, but this was low light and the EVF is not the best under those conditions.
I'll be using the combination more.