I've always been very dubious with using compatible cartridges for printers. I am never going to be 100%, until I see the clear cut facts - but thats never going to happen.
However, from experience the compatible toners and inks are only "worthwhile" if they do not have any sort of technology on them. We've got a real mix of printers where I am, and some of them have chips, others do not. As soon as we started using compatibles in the chipped printers, we started having all sorts of problems, the ones without have been fine.
Food for thought, perhaps?