I've played a little over 100 ranked matches with MMH on XBL and only encountered 3 mirror matches. I've run into at least 25 GLs, opening with MMH's f2d3 is wrecking their sweep combos at start of match.
I'm digging MMH right now. A little execution heavy but the range on his normal and strings is rediculously good. I think Im gonna main him and relegate Sinestro to my secondary.
One problem with MMH is for some reason I have the hardest time dealing with Bane and Grundy, their armor is just too much to deal with. So for those matchups I have to counter with Sinestro for now. I really need to figure those MUs out.