Some of the stuff on the forums is fairly accurate, you still get the odd nub shouting "omgz fake! shopped!" etc, similar stuff (out of the Chinese factories) was very accurate prior to the 3G launch, so I've no real inclination to doubt it (magenetometer, autofocus cam) now.
Others are fairly logical assumptions given business arrangements (OLED screens from the partnership with LG), but we won't be able to tell until the keynote unless there are more factory leaks.