Well, I've mentioned my opinion before (if you know it it helps, if you don't go straight to ancient Greek) but I must admit myself surprised by some things I've read.
Aristoklh a different language? I was never taught of AG this way and using modern Greek to explain ancient Greek has always been one of my favourite tools that I miss when explaining things to non-Greek speakers. And I can't understand that point about oral language I'm afraid.
Perispomenon, in general modern Greek sentence structure is just more simplified and analytical than ancient Greek
Other than that it follows the same structure as ancient Greek is less freely (and the loss of the infinitive and severe restriction of use of the participle hamper us something dreadful comparatively speaking but, again, it only means that we go for more analytical structure).
As for the ancient words well, the trick is to forget the third declension and think of the AG accusative as the nominative more or less in these cases
True, it's not as if our vocabulary hasn't changed along grammar but in general Greek is rather "conservative" really.
Pronunciation? God help you there
Anyway, from friends of mine who have gone either way (from one form of the language to the other) I've heard that it helped. It's too much of a bother if you are not interested in one of the two forms and if we're talking about Homeric and not classical or Koine Greek then things start looking a bit tricky but it is true that we don't expect any visitor to know modern Greek so we tend to react very enthusiastically when one does