Well, I've been playing Brawl now that my boyfriend is visiting....AWESOME!
Few comments...first, the balance is incredible. I tried every character (except Toon Link, Jigglypuff, and Wolf, due to them not being unlocked yet) and there is no one at a great disadvantage. Every character has strengths compensating weaknesses. I thought melee's balance was good, but this game's balance just...wow.
Now, the characters. Pit is definitely my favorite. I love everything about him and he fits my playing style so well. I also love Ike; he's probably the second slowest character in the game, but he's incredibly powerful and this makes up for his slowness. He also does not flinch very easily, so he can pull off those slow attacks even when being hit. My third is probably Diddy Kong...I normally don't care much for the faster characters, but Diddy is just a lot of fun because he's so unique. And he's a monkey, how can you not love that?

My fourth is Bowser...he's like Ike, in some ways, slow and powerful, except even more extreme.
I've also been able to look at subspace emissary, the event matches, and mess around with the stage builder, which is so much fun to play with.