Firefox? Compliance issues? Erm, no.
As for stability, since Firebird 0.7 I have had about 3 app crashes in total that were caused by general browsing. Add another 6 for testing other sites that other people say crash the browser.
Firefox does have bugs in of course, though I wouldn't go as far as to say 'buggy' or I wouldn't use it, because I use apps that *work* and don't have patience for ones that don't just *work*. I have one bug report open for a bizarre/obscure page rendering issue and that's it. Compare that in the past to on average I used to have about 6 Mozilla bug reports open simultaneously, which is now down to 0. Mozilla is more 'feature stable' than Firefox, and I would prefer Firefox to be 'feature stable' (as in, I don't want new bells and whistles, I want things like its memory usage improved!), but Firefox has features over Mozilla, and I like Thunderbird ten times more than Moz Mail.