Per the podcast on thank you notes a while back, I've been using them quite a bit for the past year or so and people love them.
As Mark said, "It is NEVER too late to say thank you to someone - NEVER." That thought hit me as I recently passed my 20 year milestone with my current company. I realized I never sent the people who interviewed me thank you notes. One went on to become the CEO and is now retired, the other is an EVP. So I told myself "Self, you own some thank yous." I wrote them out (per the MT format) a few weeks ago and got them out.
Last night as I was getting in my car, the EVP changed course as he was walking through the parking lot. He headed over to talk to me. I rolled down the window and asked "What can I do for you?" He smiled, shook my hand and said "Thanks for the note." "You're welcome, I'm glad to be here" was my reply. "A wise man told me that it's never too late to say thank you. I appreciate you selecting me all those years ago."
That was a great ending to my work day!