I think I am right in saying that it was previously c43MBit @ 1080p30, or something like that. What happens when you use 1080p24, is the bitrate now lower, or are you still getting the same overall bitrate at each setting?
If the later is true, you are now getting 20% higher bitrate per frame if you use 24fps.
I will be honest; I was not expecting this to be released so soon...it is good news for any 5dmk2 owner. Cannon have really made an effort here, they could all to easily have never released it.