Almost every energy source has it's bad points. If you're switching over to a different type of energy than the one you're currently using the question to ask isn't "is it good or bad" but "is it better than what I'm using now?"
As for the water issues, It's not an absolute that CSG will effect the water in any way, though it can and because of this the individual governments have their own laws about where CSG mining can occur, and the precautions that must be taken.
I'm sarcastic a lot. If I offended you I probably didn't mean to. Probably.