Fascinating topic,
Davem, I must say...
Perhaps I was lucky as a youth (oh... does that sound pretentious!
) that, having swarmed through LotR and the Appendices, I was on immediately to the
Silm, and ended up romping happily through that (though with the usual troubles of distinguishing all those "Fins" from each other), and though I don't recall the story or the prose sinking in much on the first read, the "Guide to Pronunciation" did.
I'll be honest, though... it was still a few read-throughs ere Seleborn had become Celeborn or Sírdan Círdan. It was even longer before sore old Soron had become Sauron, and Minus Tirith (as opposed to Plus Tirith) had become Minas Tirith. And then there were the Dúnedane--Vikings from old Arthedenmark!
Still, by the ripe old age of 14 when the movies came out, I was sufficiently inculcated in the "proper" pronunciation of those words that I was already correcting the pronunciations of other friends who, anticipating the movies, were talking about Seleborn and Soron.
One of the reasons, I think, that I liked Tolkien at that age, and what still holds one of the attractions for me is, precisely, the linguistic aspect. As someone who sings quite a lot of Ecclesiastical Latin on a regular basis, but who spent last year learning Latin with a Classical pronouncer, I'm particularly susceptible, at this point, to the difference that a hard "C" makes versus a soft "C." Although Tolkien may not have condemned those who pronounce the names wrong--a knowing bit of tolerance from the expert there--I like to think that, even if it doesn't
matter, I'm getting a better, more authentic, experience by reading the words the way they "actually" sounded in Middle-earth.