Sounds like great fun Piratecat.
I too love the liberal use of comics standbys in game, if you play with anyone who is even a remote comics reader from way back it's so easy to put things into an understandable perspective, and to generate a nice feel for the game that everyone can easily "get". I've loved running/playing in our supers games, though we havent used M&M (which I should check out one day).
We are currently running a side campaign that we are calling the "Centurions", which is a string of loosely-connected stories (issues), each one covering an event that happens within a 5-year timespan of history, starting with the year 1900 when the "event" caused people to start manifesting super powers. We try to mix in pulp coolness and real world events/people with just enough spin to feel like "it could have happenned that way". Each issue is not supposed to be more than 2 game sessions. This way we can get other players to pick up a night or two with a simple story and let our main GM and me take a little break from time to time. It's been fun so far. We've fought the Chichester gang in New York, went to work for Teddy Roosevelt, met Einstein and Edgar Rice Burroughs, fought Prussians in hot-air balloons and accidentally killed Tarzan.