It doesn't seem to me that iPhoto was intended to be an editor. Perhaps some enhancements will come, but there are other applications out there that will always be better. In any case, I believe iPhoto is an awesome app, especially nice for photo organization and ordering prints.
Also, I agree that GraphicConverter is a good, inexpensive choice for doing what you need to do. Personally, I prefer Photoshop, and use it often in 9.x (for now).