The answer to the question is "it depends". I shoot in raw so all my photos require some "tweaking". As to how far I go, "it depends" upon what I am trying to achieve with the image. All photographs, from the beginning, have been manipulated in some fashion. Even before processing, an image is manipulated from the point-of-view of the photographer.
I have had times were I have been forced to use Photoshop for some heavy manipulation. We you get desperate, You have to do what you have to do. But otherwise, keep its simple, its also quicker that way.