The public interest pursuit is focused more on prestige rather then money.
A TDY of service in the JAG corp often leads to huge networking, connections with Gov and NGO people, and secure placement within the public sector afterwards. Former JAGs also often get dibs on prestigious foreign service, which can then lead to international legal positions down the road.
A caveat though. I've talked to a few former JAG lawyers, and I also have a lot of military in my family. I'm also considering JAG, but I want to see how well I do in 1L first. JAG positions are often limited as well. http://www.jag.navy.mil/http://www.jagcnet.army.mil/http://sja.hqmc.usmc.mil/http://www.jagusaf.hq.af.mil/