I just received the firmware update for my 5D MkII "fixing" the black spots and banding issues.
Prior to the update I'd taken about 2200 shots, including about two dozen at dusk with point-source lights. Blown up on my 46" Sony Bravia LCD at 1080, I can't find any black spots. I never used RAW2, so there was no chance to experience any banding, since it was only experienced in that format.
The firmware update was easy to install; however, since I experienced neither problem, I can't report an improvement.
Anyway, the update's out there for anyone experiencing this problem.