Im in the Pre-Open beta for Overwatch on PC, and there is a definite skill gap that I see in game, but I don't think that is due to shoddy MMR, but more to do with Blizzard wiping everyone's stats from closed to open. The System works, but because everyone was returned back to zero you get matched with SkillGodz. I feel that if you have a long beta, such as with Overwatch you kind need to let the higher skilled players keep their MMR, so newer players arent scared away from skill gaps.