M&M is basically a d20 total conversion that fixes a LOT of the inherent problems with the d20 system, vis a vis the core rules. It's awesome, flexible, logical (within certain genre conceits), fun, true to its source, & above all, awesome. Did I mention that it's awesome? Because it's totally awesome.

Also, I was curious as to what you meant when you said that you were chased off of D20 Modern by its quirks. What quirks annoyed you? It might help to determine what kind of game would best appeal to you.