George W. Bush didn't invent signing statements, and the fact that he used them at all is really not the issue. The issue is that he used them many times more than any previous president. So, tying Obama to Bush because he's used one of them shows an ignorance of presidential history. "Look, look!..Obama is just like Bush!.
I'm not in favor of signing statements, but when Congress writes in supervisory authority over Cabinet-level spending that isn't allocated to them, how do you handle it? If they want more authority, they need to write the legislation and have it vetted Constitutionally.
Bush used signing statements to build more authority for himself. Obama is using one to prevent Congress from acting like Bush. Obama is defending constitutional separation of powers, not adding more powers to the executive branch.
This signing statement appears to be a message from the Executive Branch that it will not adhere to "legislative vetos". A legislative veto is where Congress passes a law, the Executive signs, but part of the law is a requirement that Congress has authority to overturn or direct executive action.
The language of Obama's signing statement says "numerous provisions" of the law "purport to condition the authority of officers" to spend money "on the approval of congressional authority." Obama appears to be saying that Congress passed the law, he's signing it, and now Congress doesn't get a say as to how he executes the law.
This type of signing statement is vastly different in nature and scope than Bush signing statements, whereby Bush, upon signing a measure passed by Congress, stated his intention that he would not execute the law as written, contrary to his obligation as the executive.
The most best example of this is occured Bush signed into law the ban on torture. He attached a signing statement which said he would "construe [the law] in a manner consistent with the constitutional authority of the President ... as Commander in Chief." Recent memos released in the last of couple weeks have revealed that Bush interpretated this alleged "constitutional authority" as unfettered and without limit. Unlike the Congressional veto, there is no Supreme Court precedent that would back any interpretation of law in this manner.
Perhaps the best question is to ask, "is the signing statement consistent with the Constitution?" In Obama's case, he is saying the President can ignore a portion of a law that gives Congress executive authority. In Bush's case, he was saying the President has unlimited authority as Commander-in-Chief and that authority gives him the right to bypass laws as he chooses.