It has no "official" weapons suppliers. It has no strong allies (although there's good reason to believe that it is currently backed by Saudi Arabia). It has no capital, no diplomats, no ambassadors, and has not been recognized as an independent state. That said, the leaders of IS (former Ba'athists from Saddam Hussein's regime) are intelligent and competent. They have crushed the Iraqi military in nearly every engagement. In part, this is because Donald Rumsfeld made the disastrous decision to disband the Iraqi military after we conquered Iraq. Iraq's Shiite government has a brand new military with no institutional knowledge. Their morale is abysmal. They, quite simply, don't know how to run an effective military. In fact, an Iranian has now been given control of Shiite Iraq's military because the Shiite Iraqis recognize that they have no ability to wage war with their military in its current state. The vast majority of the folks with institutional military knowledge in Iraq are Sunnis (former allies of Saddam Hussein), and they are now running the highly-effective IS military.
IS remains weak, but, as I said in the OP, IS is an existential threat that I would rather deal with now before it grows any stronger. In effect, I agree with you. IS is the real deal, and it needs to be destroyed. I don't think I am crying "wolf" when I say that.
-Laelth