To the OP:
There are two things that your 5D Mark II lacks that I find I need in a light meter:
1) a built in incident metering mode; and
2) a flash meter function - particularly one that reads in incident mode.
You can kludge up a pseudo incident mode with a grey card, but it is far from convenient in comparison.
I would think, given the wide variety of cameras you have and use, that it would be advantageous to you to standardize on a single meter, and then calibrate your various cameras and lenses to that meter.
The 5D Mark II is a system, that may involve different lenses, metering patterns that may vary with different modes and other variables.
How well does it serve you if you have to account for those variables?