I agree 1o0% with the other posters. tcpt is a faculty member at a very respected program so I would definitely listen to what he has to say. It's definitely not going to hurt. I read about a program that actually keeps copies of thank you notes in the admissions file. I'm sure a note alone isn't going to get you in, but if it comes down to two more or less equal applicants I bet it could help as a tie breaker.
This is only anecdotal and concerns a job interview, not a grad school interview, but I think it's still appropriate. I interviewed for a job a couple of months back working in health education that I was probably underqualified for. The interview seemed to go great, but I had the feeling that I just didn't have enough experience in that particular field. Not long after the interview I emailed them to thank them and to ask for feedback. It was my first "civilian" job interview since leaving the Army and I imagine my interview skills were a little rusty. I didn't imagine I would hear anything back, but about a week after the interview I received an email that basically said they were initially going to give the job to someone with more health education experience, but they were impressed with the follow-up email. It showed my dedication and passion for the population the job would be working with. They offered me a follow-up interview where they pretty much offered me the job on the spot. I firmly believe that email got me the job. Like I said before, sending a thank you can't hurt and will probably help.
