Peter Bergen, author of a new book on the Bin Laden raid, has an article in the New York Times discussing how warlike the president has been in practice, despite what Republicans and perhaps even Democrats expected from candidate Obama. It is certainly correct that Obama has been quite willing to use force abroad, but mainly semi-secret force or actions with low risk of American casualties. That's probably an accurate reading of US public opinion that still wants to punish bad guys overseas but doesn't want quagmires or body bags.
I think the president deserves credit for approaching his use of force decisions carefully and deliberately, not just following a gut reaction. What he hasn't done sufficiently, however, is to bring Congress into the process.
On the other hand, Congress as an institution and congressional Republicans in particular have a default setting that prompts immediate criticism and then reluctance to provide a collective response. In short, Congress continues evade the responsibility that comes with its war powers. If Congress favors military action, it should say so in decisive votes after due deliberation. If lawmakers oppose military operations, they should find a way that a majority supports that sets conditions or limits on presidential action. What it shouldn't do, but did in Libya and is now doing in regard to Syria and Iran, is to complain and criticize but fail to legislate.