[David L.]

I (have) received your letter.'
Don't always try to find a difference in meaning between simple past and present perfect because there often isn't any difference.

I think this statement is misleading, 2006. It presupposes that, as in your example, our communications verbal and written consist of isolated sentences, when in fact there is a much wider context in which words are chosen and spoken.
I received your letter. Fact. It arrived. I didn't know you were going to write to me, and now I am replying.

I have received your letter.
The person may write these words in isolation, but in his choice of the present perfect, he is writing from the context and mental framework of:
"I have some very good news. As you know, we have been unable to proceed with your claim for the Vanderbilt inheritance until we had proof of your paternity. I have (now) received a letter from Somerset House with your birth certificate, and so I will immediately lodge..."

I also disagree with:
Tell me some of the good things that he did since you have known him.

Will it be fine with "did" and what will it mean? Yes it will, and the meaning is the same.


'Since' can only be used with perfect tenses :"Tell me some of the good things that he has done since you have known him."