The Power Level limit has become a limit only for PC's. Villian's and NPC's ignore the restrictions. The GM is directed to review the power level of the villians by looking at their highest bonus/save DC. Beyond that thought the sky is the limit.
Another quick note, PL now only restricts Attack/Defence Bonuses, Save Bonuses, and Damage DC's when it comes to powers. Things like movement powers are no longer restricted by the PL. They also added a power called Super Strength which allows you to carry increasingly more "stuff" but doesn't affect your combat stats. Lets you have guys picking up battleships with out breaking play balance.
My only peeve is that the powers section is a mishmash of effect powers and descriptive powers. For example the Blast power is in the book 4 or 5 times just renamed. A number of the powers are essentially "use X power with this bonus/limitation". I can see why they tried to do it the way they did but the result is very muddy. I think if they had split ip the Powers chapter into one chapter detailing the core game effects and then a second chapter showing how to build powers with the core game effects it would have worked better.
OK enough slaps, here's the big benny. M&M 2.0 does something that Champions can't. It does absolutes, that is to say if my guy is invulnerable to fire he can be mechanically invulnerable to fire. Can't do that in Champions so I give M&M the big thumbs up here.
Jack
P.S. as to the actual topic (heh) go with M&M 2.0. Magic of Eberron is a great book but you'll do more with M&M 2.0.