But there's so much more on today's web than standards...They just need to adhere to the standards which have been unchanged for so many years. I can only tag as total irresponsibility the fact a browser still comes out these days without FULL standards compliance.
Displaying images, for example, supporting proper fonts, and so on.
And the standards themselves, as many as they are, are big and complex and difficult to implement.
No browser today has 100% standards compliance.
It doesn't really matter that much, though, as long as the developers strive hard to achieve it.
But then there's the question of speed and memory usage - things important to many people. A browser shouldn't eat too much memory (*cough* IE7 *cough*) or be too slow (*cough* IE7 *cough*).
And I think the devs at Mozilla has done a great job with FF3.
I hope they keep it up!