I've seen the comment farther up in the post about the Simplex parts being junk many, many times. All I can say is I still had the original Simplex ones on mine and they never failed me. Really to me not something to worry about. These are friction shifted so if one failed I would have just put on any ol' derailleur that would do the trick.
Maybe the comments about Simplex parts always failing is in the same vein of Campagnolo delta brakes " don't work". I know for a fact that isn't true if you know how to actually set them up.
Only the 3 pivot version and work exceptionally well.