I want to go down this route when I graduate too.. Our hospital just hired ACNP's a year ago. I have talked to them an absolute ton, and I admire everything they (want) to do. They came from Texas, where they pretty much worked as intensivists, helping physicians do the more tasky work (central line insertions, art line insertions etc.), help "bridge" all the specialties that worked on pts, some diagnosing etc. My understanding was they still worked with physicians and never truly independent like a FNP would in a family care clinic. They also produced massive amounts of education for the ICU nursing staff, and continue to do so here.
The only problem is depending on the location, it seems the west coast hasn't accepted ACNP's as well as the east coast. Although they were hired here to work in the ICU, our intensivists actually are blocking them at this time from working directly in the ICU. Instead, they work as hospitalists until a decision can be reached on how to get them into the ICU proper without stepping on too many toes. :S