I’ve worked out on them to try them out, but I do not teach on them, and I do not think I would spend money for Pilates equipment classes. There is a facility I know that invested in 4 reformers and ended up putting them in a closet because they did not have enough use to justify the space they took up, nor could they keep an instructor as they didn’t get enough students to pay enough to keep them. On the other hand there is a Pilates studio I know that has done so well they have expanded two or three times, and they have all of the equipment. Unless I was to certify in Pilates and work in it exclusively either as a student or as a teacher I would have to think carefully about any of the big equipment.
I think they can be effective, but I generally prefer the simplest, lightest and least expensive equipment. My favorite piece of Pilates equipment is the ring.
However for students who really love the discipline of Pilates, and who want to make that their primary form of exercise I would say everything I have tried has been effective and well designed. I do like the Reformer, and I guess if I had a studio and knew I had a market for it I might go for that one as it seems the most adaptable of the big equipment.
The other thing I enjoy for pilatese-esque workouts is the Bender Ball. Leslee Bender, the inventor of the Bender Ball, has a long background in pilates and there are several DVDs for her ball used in conjunction with pilates. Since I don’t teach a pure pilates class, I use it for “core” and circuit classes.