There's been lots of speculation about which browser will get Acid2 working first. I'd put my money on Safari. The problem is that we're late in the Gecko 1.8/Firefox 1.1 release cycle and there are a couple of bugs that would be quite a lot of work to fix, and introduce significant risk, and they're just not as important as other work that we have long planned for 1.8 and some other strategic work that I'll blog about soon. We will get to it in 1.9.
I'm sure some will seize on this as an opportunity to say "Gecko developers don't care about standards" ... they're simply wrong, as anyone can tell by looking at the huge number of standards compliance bugs we fix in every release. And keep in mind that if everyone's #1 priority was always standards compliance, Firefox would never have happened.