Wedding ISO settings

Just curious what ISO other wedding videographers are using when shooting with a 5D Mark II or comparable camera. I've been afraid to go over 800 ISO, but since most wedding receptions and often times the ceremonies, are fairly dark, I have hard time shooting even at f/2.8. This greatly limits the lenses I can use.

highest I go at reception is 2500iso at 5.6

I go to 1600 on the mark ii without a second thought. Usually with fast glass (1.2), that's more than enough to get stunningly well-exposed footage in even the darkest environments.