I think one issue might be how the names are presented.

I look at 'Conchobhair' and I go "Wait, what?", but when you say "Con-ho-var", I go "Oh, like Connovar in David Gemmell's books" (and I didn't have any pause wondering about pronuciation with those).

There's the issue that whilst we're using something that (may be, I don't really know about the subject enough) be based off the same alphabet as the Celts used, the usage has changed a lot, so spelling things as they did becomes less understandable.

Thus, I think either writing it as it sounds, or having some clue in the book as to the pronunciation would be a good thing.