I own this and really like it. It is a lot of money, but compared to other pilates chairs its a steal, IMHO.
1- It is sturdy, for the most part. The exception is the foot board that seems to be just a piece of vinyl-covered particle board, and the corner of it bent the first time I used it (before I got the hang of how to open and close it easily).
2- The springs are strong, but flexible enough that I can stretch them enough to put them in the two resistance setting without strain. They are bigger in diameter and less compactly coiled than the one I remember from reformer at my pilates gym, but I really don't know if that means anything.
3- The exercises are definately doable - I can't think of any where my weight, or even being heavier than I am now, would have caused a huge issue. The "pull-up" or whatever they call it (feet on pedal, hands on seat, lift hips to sky) might have been hard to do all the way at my start weight, though, but its such a good move! It gets up higher into my upper abs than anything else I've tried.
All in all, I'm happy with my purchase - its a nice machine, and it folds up well for storage. Its a bit confusing to maneuver at first, but after a few uses I seem to have the hang of expanding and collapsing it. My only complaint is that the workout videos move slowly - a lot of time spent listening to explanations, which is fine when you first start, but gets old really quick. I wish I used it more, but I can't blame the equipment for my lack of motivation...
Really, really loves her forum chicks, and wants them to know it!