Delivering the letter in person, dressed appropriately of course, shows a keen and sincere interest, as well as giving the opportunity to 'be seen' once more, & provides one with a chance to observe the work environment 'in action'.
Also, a 'hand written' thank you has a very powerful and memorable impact vs. an email. Personally I always hand write a Thank you for a in-person interview, and email one for a telephone interview.
Take a control position once you nail the interview and keep in mind that 'inter-viewing' is always a 'two-way street'.
A thank you letter is like breathing to me, it is a common professional courtesy, and another marketing tool for you to shine with your writing abilities, and keen interest in the position.
When you do receive the dreaded 'merge reject letter', I would suggest, (depending on the level of the position and what transpired during the course of the interview in terms of 'rapport' building),
* ask the interviewer direct questions as to why you were not chosen, and
* 'ask for a referral' to any firm or professional they know that may need someone with your particular skill sets & personality profile. At the very least, 'keep me in mind'.....
Remember, THEY contacted YOU for an interview - obviously you did something right to make that happen - they were impressed enough with you on paper - why wouldn't another firm be.....
