I have a Stereo Realist. It is big, heavy and a bit clunky to use, but it takes great pictures. The worst part is cutting the film and mounting the two shots in the slide holder. This is such a pain, I recall reading once that someone was offering to pay for someone to do it for them!
Several years ago I bought a pair of Oly 35RC's and a pair of the little Panavue hand-held viewers. The full size 35mm slide should give a a better quality, and the optics of the Oly's are well known. I have never gotten around to making the mount for either the cameras of the viewers. :-(
Taking a 3-D photo is very different from a 2-D --> the subject matter, composition, everything. So it is difficult to switch between the two. You have to be in the right mindset for each format.