First, did anyone else laugh when reading this thread and realizing that it could only be medical students/type A personalities who would write so much on such a topic as thank you notes? Or perhaps it speaks to the stressfulness/insanity of the match process that causes us worry so much over such a trivial thing?
Second, I am a big fan of handwritten thank you notes on nice cards UNLESS the interviewer and/or PD specifically gave me their email address OR I was explicitly told by the PD NOT to send thank you notes. (This happened at 2 different institutions.) But even then, I emailed a short thank you to the interviewers, not the PD as I did not want to appear like I cannot follow directions.
Third, for medical school interviews, I tried to put something personal in each thank you note to my interviewers, but this time I had a more difficult time thinking of something unique to write in each note, so I just said basically the same thing in each, just in different words. I did make a point, though, of writing what I specifically liked about that particular program, especially if I knew that I was going to be ranking it high. I figured that instead of trying to sound as if I were trying too hard, a simple, straightforward thank-you note would be best.
Last, I only told 1 program that I will be ranking it high. I plan to write another letter to the program I eventually rank as #1 letting them know I have ranked it #1.