Yeah, I am a 2nd year IRTA at the NIH. I love it, and I hope to publish soon. As for clinical experience, it depends on the lab. Most of the labs in the Clinical Center of NIH have clinical research trials, and the PIs in those buidlings are more likely to offer you clinical experience. They may conduct translational research. If you are looking for clinical experience at the NIH, you might wan to look for 1) the location of the lab (i.e. building 10 Clinical Center), and 2) the PI's degree. Most of those that conduct clinical research are MDs, and MD/PhDs. PhDs are more likely to do basic science. Although my PI is an MD, she conducts basic science research. But she is very helpful with the medical school admissions process!
I am no means an expert, and you should keep asking around. But I hope this helps.