I have been using ML to shoot 7 and 9 bracketed sets for HDR photography. After doing this for a few weeks, my T2i developed a severe exposure problem when shooting through thew viewfinder. All shots were over exposed by 2+ stops. (Shots taken through LiveView use a different metering system and were perfect.)
I sent my camera in for servicing and it came back to me in perfect working order. Didn't use ML for some time out of fear it may have done something wonky to the camera firmware or settings.
Started using the 11.11.11 release of ML this weekend for more bracketed shooting and after one day out, my camera's exposure is suddenly "broken" again. This time, all viewfinder shots are underexposed by 2+ stops. I have removed ML completely, reflashed with standard 1.09 firmware, reset all settings, etc. Nothing helps. Sadly the T2i CMOS battery is inaccessible, otherwise I'd look at removing that as well for a COMPLETE reset of the camera.
I think the ML coders need to look into the serious possibility that something in the HDR bracketing is messing with the internal viewfinder exposure system.