I'm a huge fan of SFP, and just read the whole archives of this in one evening. It's tons of fun. I'd read comic books if they were like this.
Wonder Woman is my favourite character in this so far, by a long shot. She's smart, perceptive, gutsy, but she has her own issues that she benefits from talking out with friends (the "I don't want to be a princess" thing). Superman's adorable. Batman's annoying but hilarious. J'onn (probably the character I know least about, and I only know about any of them from movies and TvTropes) is great.