I'm a 2L at a regional university and I'm considering an LLM in international arbitration/alternative dispute resolution, any suggestions or advice about the usefulness of such a degree and job prospects?

I would advise Pepperdine University, if you're focusing strictly on ADR, Harvard has a very strong Negotiation and Mediation Program too.

also, University of Missouri-Columbia. Tied in ranking with Harvard in 2008 (No 2 right after Pepperdine)