ArXiv is incredibly useful for research, but I think people also use it for a sort of "I posted it to arXiv first, therefore I solved it first" kind of thing, which imo can be misleading at times, if not everyone follows that. Also there is the eprint.iacr.org which seems to do the same thing, except for cryptography (or is it cryptology?), so I'm not sure if every important preprint in that topic gets to arXiv.
> I think people also use it for a sort of "I posted it to arXiv first, therefore I solved it first" kind of thing, which imo can be misleading at times True, but I don't see that fights over precedence are unique to ArXiv either, or even made worse by it, no? I mean, at least now there is an unambiguous date-stamped public place to cite in this kind of fight. And those fights provide a built-in incentive to put stuf…
I'm not familiar enough with other methods of preprint publishing besides arXiv / eprint.iacr, but you may be right that it is not unique to arXiv.
My personal preference would to be to have bits of research done through something like git, so that work along the way can be seen, otherwise one may solve a problem and then be 'out-arXived' by someone who spends an all nighter tex-ing your solution (this is a hyperbolic example, but I think the idea of the potential flaw in the system should be clear).