What does signing the NDAA really mean?

Lets recap: For seven years the Bush administration flouted the constitution committing a series of criminal acts including torture, murder, kidnapping and war crimes. In an attempt to provide post-facto justification for these crimes, the Republican faction in Congress accompanied by some of the usual traitors insisted on a clause in the defense bill (NDAA) purportedly granting the President the power to commit some of the clearly illegal and unconstitutional acts.

Obama has now signed the NDAA with a rider to point out the rather obvious fact that Congress cannot grant unconstitutional powers to the President, let alone force him to exercise them.

People are telling me that this is some sort of epic cave on the theory that a future President might choose to go round imprisoning people without trial, in short behave just like Bush did. So what difference does signing the NDAA make?

The only difference I can see is that the courts might be more inclined to keep their oath to defend the constitution when faced with an abstract grant of clearly unconstitutional powers to al presidents than they have been when faced by the criminal acts of the last president.