safari's web inspector

i usually use firefox when i'm working with xhtml/css because it renders consistently and the dom inspector is pretty handy. the rest of the time i use safari, so i end up switching back and forth a lot. while i was working, i ran across safari's new web inspector and it is awesome. there's probably some similar plugin for firefox (i don't really do web stuff often enough to find out), but this little addition gives me one less reason to ever move away from safari...