Re: Some issues remain...
> surely this can only be used on satellites that will 100% burn up during re-entry.
In which case, even a de-orbit burn won't be much use, will it? And as they were looking for an alternative to a burn that specific objection is hardly a failure of this design.
But most of what is up there will burn very nicely (if you are thinking of the recent "unidentified lump from the heavens" your average satellite does not have large tanks).
> the risk on an uncontrolled re-entry taking place
Most of the satellite re-entries, afaik, are "uncontrolled", as the de-orbit burn may be just enough to drop them into atmosphere only as deep as required for them to experience drag to finish the job. It is only the big beasties, or the manned missions, where they worry about a burn large enough to get them down right away and in a planned location.
> but also the issue of how "irradiated" any solid pieces will be, which could cause a health issue.
Stuff in space certainly gets irradiated more than stuff down here, that mostly means that the space blobs are killed, which is a plus, healthwise (so only the really strong ones survive to get down here - look out, Steve!). It doesn't mean the bits of debris are themselves radioactive. My wife irradiated people for her work: they were okay to be around afterwards. Unlike the ones stuffed full of tracers, which weren't there to irradiate the patients as much as causing the imaging equipment to react: it was preferred that they hung around until they had, how to put it, safely expelled most of the materials.
 as always, links to material that corrects me happily accepted.
 but stay away from, say, active volcano plumes or spending too much time down deep holes in granite, or ...