Well, the new wave of DLC is out, and Lucas, Roy, and Ryu are indeed playable fighters.

Ryu is very interesting, and very heavily based around his Street Fighter play style. He is powerful, versatile, and combos well. But he isn't the fastest character, he's vulnerable off platforms, and he has no reliable way to hit behind him (the closest he gets is his reversible focus attack). So he's especially vulnerable in free-for-all fights. Which makes sense, because in Street Fighter, he always faced his foe, and never needed to strike behind him.