Bruce getting darker is a natural and realistic consequence of his life, but it's an example of injecting more realism not necessarily being a good thing. If the main character is no longer enjoyable to read about, what is the benefit of it? It's why Morrison's run was a breath of fresh air when it first came out as far as Bruce was concerned.
I know dark edgy Batman is very popular and it seems to have worked for the character. For me though it's because it appeals to the lowest common denominator and has made the character less interesting/engaging, not more.