You'll have to forgive me, because it's been over a decade since I played any P&P RPG...
That said, I was introduced to the D20 system via D&D 3rd ed, and I always found I liked it. (Maybe because I was introduced to 3rd ed after having played enough 2nd ed to be completely fed up with it...) It definitely works with M&M, and the superhero powers system is different enough from the fantasy that it really isn't just "Dungeons and Dragons with superheroes". If nothing else, I have no memories of being stifled by the game mechanics.
I also don't recall many of the games I was in, save some bits of the first, and now I am going to ramble some, so feel free to move on with your life if you've read this far. :V
My first Mutants and Masterminds character was The Pangolin, a kid with no powers who finds a metal jacket while dumpster-diving. When he puts it on, it expands to become a suit of armor that is, yes, pangolin-shaped. He teams up with a bunch of other superheroes (I wish I could remember who they were! There was definitely a sword-wielding woman named Red...) and they fight crime in the New England sister city of Freedom City, whose name I also forget.
I tell you, I did not appreciate what my GM did for us. (I was young, and dumb.) He ran game sessions as "issues" and we would have special editions now and then. He created an entire backstory for the Pangolin that I'd never even conceived of: a nemesis named something like Dr. Zoopopolis, whose thing was making robots and stuff shaped like animals. We had to fight a bunch of dudes in power suits similar to the Pangolin's at one point, even! But the one session that really stands out in my mind was the Thanksgiving special, when the city was under attack by a giant turkey robot that shot ice beams out of its mouth. Its name was Cold Turkey. Dr. Zoopopolis was a weird, weird guy.
One of the cooler things, I think, about M&M is you can add new powers as your character evolves, not just upgrade the ones you start with. As Justin, the Pangolin's alter ego, grew and fought, he started manifesting a technopathy ability, on account of his dad was secretly a powered superhero (backstory I did conceive of!) During a climactic battle with some kind of world-ending entity (I think), I got hit with an energy blast that would have killed my character. So the GM did what any good GM does: improvise.
The Pangolin's armor, which had been shown as sentient even before he was able to interface with it directly, leaps off of his body, sacrificing itself to save him from the blast. It was an epic moment; the Pangolin died, but Justin lived, and would go on to take up an NPC support role to the team as Interface, something of a Barbara Gordon character. I replaced him with a hero named Obsidian Jade who was considerably less interesting, so we'll stop there.
If there's one thing that's hard about selling the SOEP Kickstarter to folks unfamiliar with the RPG is that, well, it's an RPG. You don't have to use any of the preexisting characters or settings in the source books, and my games never did. So other than reading through their character stats as examples of what you can do with the system, I really am completely unfamiliar with the heroes, villains and environments we're going to be getting. (Minus Dr. Metropolis; he's absolutely the most memorable part of the setting!) But I'm still excited. :B