I think a general pattern is that the console should be smarter about the specific stuff people do in a console, in the browser. Every kind of DOM node should have specific representations appropriate for that DOM node, not just what falls out of some generic printer. There are array-like objects that get printed out funnily because they aren't real arrays – but {0: x, 1: y} is no more clear about the actual nature of the object than [x, y].
Why people won't code vendor prefixes into CSS tools I don't know; the obvious thing is for Firefox to ignore everything but "-moz-*" – and even then, to warn selectively (i.e., if there are old versions of Firefox that require a prefix, even if the new version doesn't, don't warn about it). Or hell, crowdsource the whole thing, when you encounter something invalid fall back on a community edited document about what is valid in other browsers, or represents a common and acceptable CSS hack. There's often good information in the CSS warnings, but there's too much useless information to find it. I'm annoyed things like LESS and SASS don't treat vendor prefixes specially either.
Why people won't code vendor prefixes into CSS tools I don't know; the obvious thing is for Firefox to ignore everything but "-moz-*" – and even then, to warn selectively (i.e., if there are old versions of Firefox that require a prefix, even if the new version doesn't, don't warn about it). Or hell, crowdsource the whole thing, when you encounter something invalid fall back on a community edited document about what is valid in other browsers, or represents a common and acceptable CSS hack. There's often good information in the CSS warnings, but there's too much useless information to find it. I'm annoyed things like LESS and SASS don't treat vendor prefixes specially either.