Well, anyone can be a populist, and I think can look at Obama's policies and say he hasn't done nearly enough to deal with housing issues or to create jobs, and has been far too friendly to corporate interests. Though, we could then have an argument about how much of that is the fault of the GOP and their persistent obstructionism.
You could also criticize him for not being a stronger supporter for peace, for not reversing the erosion of fundamental rights (e.g. Patriot Act, surveillance, etc), and for not making significant environmental progress (if any at all).
So I think there are a lot of ways to criticize him. Politically I am probably somewhere off the left side of the map, and unless he suddenly turns into a STRONG progressive, he won't get my support. I am not expecting him to.