Well, the basics are:
1) Power Level. Though this can be removed easily, I find it one of the best features. Point bases Supers games are notoriously hard to balance because its so easy to twink out a character if you want to. Power Level solves that. It basically restricts your attack and power bonuses until you raise that power level. So it's easy to quickly gauge what kind of theat a player can handle. Unlike D&D though, these power levels are EASILY removed if you don't like them.
2) Point Buy Creation: Depending on Power Level you have a certain number of points to use on your character. These points can be spent on stats, skills, feats, and super powers. Divide as you wish.
There are also new super-feats that let heroes have stuff like 360 vision, a headquarters, and the like.
3) Genre flexibility. Anything from gritty street to cosmic saga can be run with the core book. And run well. Gritty games will have a low Power Level, Cosmic High. The system scales incredibly well.
4) Power Flexibility: The most flexible and intuitive power creation set I've yet seen. If its been in a comic, they have it, and they have the ability to customize it. Also, very good rules for creating your own powers. It passes my flexibility test: I was able to make Iron Man, Thor, Dr. Strange, Batman, and Speedball all without problem.
5) Combat: No more hit points. Each character has must save against the damage done of be stunned, knocked out, or killed. Oh, and there's a new type of save: damage. So The Thing clocks The Hulk with an attack that does +8 damage. The Thing rolls a d20 and adds 8. The Hulk has a damage save of +12. He rolls a d20 +12 and if he beats Thing's attack roll no damage is dealt. If he fails by 5 or less he is stunned and gets a -1 to all futher damage saves that battles. If he fails by more than 5 there are worse consequences.
This system does a marvelous job at emulating the comics. Bunch of attacks wear down the opponent until finally one levels him. There are optional rules for hit points, but the damage system is so simple and evocative I don't see who would want to do such a thing.
6) HQ construction rules. Need I say more.
7) Amazing art. Possibly the most beautiful RPG book ever designed (though the LOTR core book and Buffy the Vampire Slayer core book are close behind it).
Great stock characters. While I have my own supers setting, I'll be using some of the villains. They're just too good. Many, like the Atomic Brain, remind me so much of the comics I read as a kid. Great stuff.
Go get this book. You won't regret it.
Read reviews of it at ENworld.org and rpg.net. They go into more depth than me here.
