When even former Presidents and sitting Presidents can admit that the ability of the President to execute people, including Americans, extra-judicially with virtually no review is worrisome, as Obama has done, there should be no dispute that the office has too much power.
There are some needs to make compromises to the new realities of our world. I don't mean silliness about a post-9/11 world: I mean that modern American society is just too big and complex to not have an executive branch that has some degree of latitude beyond what the Framers would have preferred.
But we have acquiesced some of the most basic responsibilities of our elected legislature, the people who are our closest representatives at the federal level, to the President. The fact that the President can basically declare war unilaterally is beyond the pale. Checks and balances were installed for a reason: They were designed to slow down the rate at which any decision is made to allow for deliberation and public comment, especially the decision to go to war. It should not be this easy to endanger millions of lives.