yep - MacRumors doesn't have tons of original rumors... but the ones they do have seem to be pretty accurate
17, 12 inch powerbooks
they were the first to post about the Apple music service - which now seems to be talked about eveywhere
and other specs along the way (superdrive powerbook)
which makes the most recent 'communicating device' rumor more interesting.
looprumors and macwhipsers seem to be the bottom of the barrel. macosrumors, of course in tail end.