All playable SSFIV characters will be unlocked out of the box, including Yun & Yang, Oni, and Evil Ryu.
I don't want this, I'm holding off from getting Street Fighter 4 so I can get this, but if all characters are just there I won't feel like I'm achieving anything. I like the satisfaction unlocking characters gives me.
We had our fill of unlocking characters with SFIV. Just get that.
I'll be honest, this game isn't much of a single-player experience. If you're not going to be playing with friends, I'd hold off. Go buy MK9 or something, as it has a far larger single-player component.