I haven’t looked at Firefox 2 yet, but the acid2 test you linked above looks correct for me with Firefox 3 (beta 2). Its off by a couple of pixels at the bottom, but its hardly noticeable and I’m not sure what it means.

Looking at Konqueror 3.5.8, it renders the bottom two sets (lightgray/grey and darkgray/grey) correctly, but it renders the top set (gray/grey) with different shades of grey!!