We've got 1.0.4 candidate builds. If you all can help us test these bits, and make sure we haven't regressed anything over 1.0.3, that'd be a big help. If you do encounter any new problems (issues you cannot reproduce in 1.0.3) please comment here ASAP. Thanks.
update 1:12 PM PDT oops, wrong links. corrected. newer builds were available than the one I linked to.
If you're looking for areas to test, navigating a lot of web content would be good, and going through the basic functional tests to check out various browser features would also be good.