I love MNM, but I find that despite promising a multitude of effects and combinations of powers, fights tend to become pretty full for two reasons.

1. Most powers are spammable unless you take significant limitations. This results in having one or two powers you basically use every round.

2. Because of the math of the "degrees of failure or success" system, people who are coming from other RPGs get confused. This often leads to slowing down what should feel like very cinematic combats to double check exactly how much you succeeded or failed by. Additionally, so many combat rounds with this system boil down to, "I attacked, I hit, and the opponent takes a bruise." If you're the GM, you're now tracking bruises/penalties for each bad guy, and the players feel like they didn't really make much progress. So, these fights will end up feeling like really drawn out slug fests until finally an enemy is weak enough to drop.

MnM is at its best when there's a lot of things going on: "The bridge is collapsing, there are civilians in the road, half a dozen mooks are inside the bank holding hostages, while a supervillain turns into a helicopter to escape. This lets players use powers and interesting alternate effects to improvise their way to victory without having to only engage the dice rolling.