In a post on July 5, 2006, I set forth my views on the pros and cons of LLM degrees. My post was aimed primarily at law students and lawyers who were considering LLMs as a way to improve their marketability for practicing law.
For a discussion of LLMs as means of improving your chances of teaching law, there is an excellent online post by Professor Brad Wendel of Cornell Law School. Professor Wendel's post, which is about the law school hiring process generally, has a good discussion of the LLM degree's potential merits (or lack thereof) in the academic career context. It is also an interesting peek inside the legal academy's ivory tower. I too recently went through the law school hiring process, and I find myself in agreement with much of what Wendel says. If anything, the law school hiring process is even more challenging than his post suggests.