Haveing read the additional counterpoints on this thread, I must say I have to agree with the other posters' points re Delta doing "everything it could" and the issues associated with having to attend a "not to be missed" event on the same day as travel to it.

In that context, I stand by my comments elsewhere in this thread as to how to go about writing/phrasing your letter ("reader: you are there with me" point of view and level of detail, "just the facts" but include EVERY ONE OF THEM, etc.), but I will amend that advisement to say that you should take these other comments here into consideration in terms of what you ask for and how reasonable your requests are for "what you think you are entitled to" in compensation.