The upcoming Unity 3.0 will have a 2D Sprite Engine, as you can see from the press release:
The press release makes it sound a little like the sprite engine is specific to the iPhone, but this is not the case. You can see the “inside” info here (top secret):
Creating 2D games is currently very clunky in Unity. Basically, you have to billboard textures onto planes or boxes, etc. There is no hit detection for pixels.
In case anyone misses the point, a 2D sprite engine makes Unity a one stop shop for game development. This effectively provides competition to Flash and Silverlight, as well as the folks at Garage Games, and many others.
Being able to write games in 2D or 3D, and deploy to the PC, Mac, Xbox 360, Playstation, iPhone, Andriod, and Atari 2600… where do I sign up?