I would say based on the price of a new Rollei TLR, they are indeed serious cameras, of course over the course of the last century most of the Rollei's have been quite good cameras with a very strong following.
Originally Posted by snaggs
Even in this day and age, TLR photography is very serious and a great many of the camera are great performers, as Digi Said, I have also used them handheld, on a tripod and they produce great images.
The mirror slap on the Pentax, can indeed be distracting, but there are a great number of photographers that use them quite successfully for serious work, The Pentax is a challenge to hand hold, it is a large heavy camera that just by its nature can cause you to shake due to the weight, I tried shooting one handheld a couple of years ago, with no success at all to the shear mass of the camera. So Tripod is the recommended way to use this camera.