I have been doing a bit of research and it seems that there are a lot of horror stories about using radweld, k-seal etc. on the net but they are usually from individuals who had a problem that either radweld couldn't fix, or having fixed their problem system, they later had a bigger problem and they believe radweld made it worse. Very few offered any evidence to blame radweld and I can't find any mechanics or dealers nay-saying it, but quite a few the recommend it (in moderation).
I think for the moment I will apply the same reasoning I would when using tyre gunk. It can fix a small problem, but not a big one.