There's a lot to be said about camera ergonomics here, probably worthy of a new thread. My Leica M2, Rollei 35 and (no longer working) Fuji Texas Leica all have the viewfinder eyepiece right on the edge of the camera, so it's far easier to look straight ahead, and open both eyes while doing it (especially if your nose is larger). Many other cameras, and most SLRs, have the viewfinder in the middle, it makes for awkward head and eye twists to look through as your head is not facing the subject. Probably contributes to eye fatigue too.