5D2.212 overlay display sluggish (ML Nightly May-June 2015) Similar problem on (ML Nightly March 30, 2014) but to a lesser extend.
On 5D2, after the "playback" button is pressed, I get the usual Canon playback screen. Now push the "picturestyle" button within 1 sec... the image overlay (e.g. falsecolor) doesn't come on! U have to press it a couple of times before it comes on.
Work around: after pushing the "playback" button, roll the thumb dial up one and down one. Then push the "picturestyle" button, overlay will be instantaneous!
Thanks A1ex and ML team for all the hardwork!