The four-to-six months it took for us to playtest and create characters (averaging about one test/building session a month) really paid off — we knew the rules well enough not to get hung up on them, and we had a good understanding of where possible pitfalls might lie. It helps that everyone (myself included) didn’t get too hung up on the rules (which is good because M&M’s a cool game, but very complex and occasionally contradictory, as illustrated by its 6-page errata [PDF]).
For musical support I used the Spiderman 2 and The Incredibles soundtracks, which perfectly complemented the mood we were going for. I’m planning on building on the that by borrowing a page from Dragon Magazine and going through my music collection looking for tracks I can use as musical “themes” for my different heroes and villains (e.g. “Fever Dream” from the 300 soundtrack).
All-in-all, a great outing — I’m looking forward to Issue #1, which is scheduled to run later this month.