How revolutionary was the Macedonian sarissa? If they really were incredibly effective, why weren't they adapted earlier? If they weren't a massive improvement, then what set Philip II's army apart?

Follow up question (might be too different): who equipped the infantry? Philip changed their weaponry, but was he the one paying for it? The hoplites that they replaced usually provided their own weapons, did Philip then just tell everyone to buy different spears for themselves? Seems like that would be hard to regulate.