Its hard to search for positions, its hard to find if you fit the requirements, there is no feedback. Half the time if you email the associated support address you just won't get a response, and if you do get a response they will give you a generic response and say that there is not much they can help you with.
I have never gotten a single interview from USAjobs, despite the fact that I have 10 years of relevant work experience. My advice go literally anywhere else.