We're currently playing the new Marvel Universe RPG.
Thoughts:
1. The game favors 'author stance' over 'actor stance'. In a sense, you are playing comic book writers and authors, rather than the heroes themselves.
2. The ARS system (using resource allocation rather than dice) is fairly innovative, fun and easy to play. The Panel/Page system is really cool as well.
3. The game itself needs tweaking. Incomplete, conflicting and just plain nonsensical rules abound, making house rules necessary.
4. It is definitely *not* d20. For one thing, it's not balanced (and efforts to shoehorn balance into MURPG are misguided, IMO). It relies *heavily* on GM fiat---If you don't trust your GM implicitly, MURPG won't work for you.
5. You also need to trust your GM to tell you to rewrite your character because it is too 'broken' (the system is very easy to abuse, again requiring a trust excercise to keep everyone on par).
I mentioned House Rules before. One of the biggest gripes about MURPG in the roleplaying community is that MURPG has such a poorly defined ruleset. One approach is to add rules to the system, flesh it out more, give it a stronger structure (i3ullseye does this a lot on his site, below). Another approach (favored by my group) is to remove rules and streamline the system, making it a more freeform game.
Good luck, and I hope this helped. To be honest, MURPG is the most fun gaming I've had in years, but it did require me to fully invest in the 'feel' of the game. That's not for everyone (we are losing one player because he hates the game so much).
Some links:
Marvel's site
i3ullseye's Boards
Thread on RPG.net
Another thread on RPG.net