I am also another PhD. I've resisted writing back to Realist but I need to chime in with another point of view.
Let me take on some of the claims Realist makes:
Realist: Only the best schools place students in academic jobs.
Fact: Your odds of getting a job are higher when your degree is from a higher ranked program. But you can get an excellent job from a middle tier program if you work hard and publish. And middle tier programs provide some nice opportunities that the top ranked programs don't. If you value things like helpful advisors, nurturing environments over competitive atmospheres, unpretentious folks who don't need to talk about Hobbes or postmaterialism at happy hour, and fellow graduate students who will answer your questions, coauthor with you, and share a pizza with you on Friday - the Top 50 program might be just right for you. I was accepted to a top 5 school and chose a program in the top 20 or 30. I have no regrets about that choice.
Realist: Advisers are fickle beings.
Fact: Some advisors are fickle. Many are terrific. One virtue of moving down the list from Yale or Chicago and choosing a MSU, UIUC, WUSTL, Vanderbilt or Indiana is that your advisor will give you the time of day. I had lunch with my advisor on a regular basis. We coauthored together. I could drop by his office with questions. He read paper drafts and gave comments. My advisor didn't just sign off on a dissertation. He made me a better scholar.
Realist: Graduate students are (1) essentially powerless and (2) extremely cheap labor.
Fact: I suspect this is less true as you move down the ranks. I think this is probably true at Harvard or Yale. It was not true at my Top 50 (but not Top 10) program. I worked with several different members of the faculty in graduate school. Some of these relationships led to coauthored papers. Some of these relationships came about when I sought out the professor to ask if they had work I could do for them (top down). Others were bottom up - where a class paper I wrote evolved into a conference paper with the faculty member as collaborator.
Realist: you need to go to the best possible graduate school.
Fact: You will benefit from going to a Top 50 program. Moving up the ranks helps but has diminishing returns. I think it is reasonable to consider quality of life and other such issues. Graduate school is often depressing. You will be stressed out. It will be nice during these times to have the things that make you happy (mountains to climb, waves to surf, good restaurants, whatever).
Realist: You should understand that you may not have a good chance of landing a tenure track job.
Fact: This is true. The job market is hard and stressful. A lot of factors are beyond your control. I wouldn't necessarily go to grad school at a program below the Top 50. If you only get in at a low ranked program, seriously consider transferring after the MA degree.
Realist: Do not choose graduate school based on who you "want to work with."
Fact: Do not choose a graduate school based on a desire to work with one person. This person might leave. Or be crazy. But it is reasonable to choose a program that has several people with research that interests you. You don't want to end up at a school where no one is well suited to advise your dissertation.
Realist: Graduate students very seldom "work with" an adviser.
Fact: Many advisors coauthor with students. It is reasonable to ask faculty if they coauthor with students and to look at their vitae to see if they have worked with students. Working with an advisor is usually a great experience. Not all experiences will produce dividends (research papers), but they always have rewards - learning new things, gaining skills, referrals to summer research work. The responsibility lies with you to seek out collaborative experiences in most cases.
Realist: Likewise, funding matters. My general advice is that outside of a top 40 institution, you should not go to graduate school unless you have a full ride and a stipend large enough to live on.
Fact: This is true. Look for at least five years of guaranteed funding. Ask about summer money.
Realist is right to say that grad school and the job market can be tough. But as others note, hard work is more important than institutional prestige. If work hard in graduate school and invest in producing research and gaining skills, it won't matter much where you got your degree. Your Ph.D. might not get you a Harvard job, but you can be competitive for most tenure track jobs. Get your work published. Write an interesting dissertation. This is the most important. One can easily search the websites of political science departments to see that smart, productive people from places in middle tier programs can get jobs at fine tenure track institutions. Average scholars from these places won't get top tier jobs, but an average scholar from Harvard might not either.