I think the pre-order skin thing they're doing is perfectly acceptable (full disclosure: I did pre-order it). It's a small, non-essential item that doesn't affect gameplay, it doesn't cost extra money, and it offers a neat bonus gift to people who buy new. It's like the little giveaways they do at the theater or sports events to the first so-many at the gate. Sometimes those have a variety too, and you don't really hear people complaining that they didn't get ALL the bobblehead dolls or whatever for going to one game.
But the Catwoman thing does kinda rub me the wrong way. A good portion of the marketing has gone to advertising Catwoman as a playable character, and to announce so close to launch that only people who buy new can play as her without an extra fee seems like kind of a dick move. It's like a sports team saying, "OK, we've played to the end of regulation, if you reserved your ticket, you're fine to stay, but if you paid at the gate, you gotta go back and pay an extra $5 to see overtime or you gotta leave." Sure, you don't have to play as Catwoman to win, but for those of us who were looking forward to playing as her but can't afford to buy new it's kind of a kick to the balls.