NPS Volunteer gigs

I've been looking into NPS volunteer work in one of the major western National Parks. You generally get some kind of housing, a uniform, and often a small stipend--which means that your bottom line is about the same as working for a slave-driving concessionaire who pays you minimum wage and then deducts for everything, leaving you with a paycheck that isn't enough to buy a new pair of socks.

The big difference is that the NPS volunteer positions I've seen involve many of the same duties as a park ranger, i.e., interpretive functions. It's more engaging and cerebral than scooping ice cream or cleaning toilets all day, and it looks good on your resume if you're planning to apply for a paid position with the NPS later on. And of course, these volunteer gigs carry the same "intangible fringe benefits" that the indentured servant concessionaire positions do--that of living and working in a beautiful place.

Does anyone here have experience with working as a NPS seasonal volunteer? Any insight/shared experience would be most welcome.