I am an NIH postbox right now and I absolutely love it. Your experience heavily depends on your lab. For example, I don't have my own project, but I work closely with a postdoc on her projects and help her out, and I still feel as though I am gaining tons of experience and am growing as a researcher (I was also a psychology major and had only a year's worth of lab experience before this). Another postbac I know, however, is in a smaller lab and pretty much runs his own project directly under the PI.
So far, most of my interviewers loved talking about my research. I am applying this cycle and started this position in August, so it is not in my application and I have only been able to talk about it on interviews. The two schools I interviewed with that didn't really care were very community and clinical oriented. However, when I mentioned my NIH position to other schools I interviewed with that had interests in research, my interviewers seemed very interested and asked me a number of questions that I could answer really well (however, I think this ties in with what other posters have said about the importance of being productive).
I would highly suggest the experience if you can. The funding is phenomenal (so far), the research that is going on is crazy, and the access to resources is even more ridiculous. If you have any questions, please feel free to PM me! I love talking about my experience here as long as it can help others in some way!
