Despite the length of this thread (27 posts and rising), there is a great deal of agreement. I think we all agree that the present perfect is a present tense, and that the situation (action, event, process or state) denoted by the present perfect verb began, if not ended, in the pre-present.
Pokemon’s suggested explanation of one sentence appears satisfactory: "The period of time during which the action has taken place isn't over yet’. […] Otherwise past simple would have been used.“ However, if it were to cover all uses of the present perfect has taken place would need to be changed to started.
The major issue appears to be slotting individual utterances into categories such as experiential, existential, resultative, etc.
I’ll just note three problems that will make complete agreement on the subject very difficult:
1. There may well be a good deal of category overlap in many utterances.
2. The categories themselves do not actually exist. They are simply labels created by grammarians attempting to explain situations in which the present perfect has been observed to be used.
3. To say why the present perfect is used in an utterance is possible only if we have the context. Take these two examples, for example:
a. I have done many exciting things in my life: I’ve climbed Mount Everest, I’ve sailed the Atlantic, I’ve watched Hockney paint and I’ve heard Chomsky lecture.
b. I think you misunderstand what writers on TG mean by ‘Surface Structure’. I’ve heard Chomsky lecture, and it is clear to me that the term means…
The two clauses in bold are identical in form, but if we are working on categories, then I think that that the present perfect in #a is experiential, and that in #b is resultative.
Another, less important problem is that I have been to is an idiomatic expression; have been conveys a meaning different from that of any other form of BE.