You have some good points concerning Angelopoulos' choir and musical style in general, but the research he and his mentor Simon Karas, have done and the the effort they have put into finding and analyzing long lost ancient manuscripts, is overwhelming, I respect them for that:
Well, you're on ground zero, and I live across the pond, so your experience means something to me...I'm stuck working from recordings and books, and a handful of live psaltes (albeit some good ones--no one publicly known, though). I generally avoid historical-theoretical discussions, because I am not familiar enough with the literature. My understanding of the whole thing is that in the first half of the last century, there was a whole gaggle of musicologuists, Greek and European, butting heads over what the True Greek Tradition was, and Karas more or less came out on top. I haven't read his book, so I have no positive or negative criticism of it.
I try to keep things centered around piety and oral tradition rather than manuscripts. The research into medieval Byzantine chant is very interesting, though.
Angelopoulos is a bit of a puzzle. The EBX's interpretations seem to have been gradually getting more extreme since they were founded. I'd have to go back and listen to them more, since I haven't for a while.
Again, I'm talking about contemporary practice here, not theory or history.
I agree with you, Angelopoulos has become more of a theoretician in the Byzantine Music lately (to put it bluntly, as one psaltis I know has put it, "his chaning nowadays does not emit insence") but his contribution in a deeper understanding of the neumes who had been forgotten (or pushed aside) by the practical chanters, can't be nullified. The golden rule IMHO is to follow the classic interpretation which has been traditioned ('xcuse my neologism) from generation to generation on one hand, and at the same time to not disregard the fresh (and interesting) air Angelopoulos has brought into the *cough*static and moldy*cough* world of Byzantine Music in Greece. It's good that we can judge Angelopoulos harshly but at the same time we should not forget that before Angelopoulos, the norm was to hear polyphonic "I-presume-it's-authentic-western-music-and-if-it's-not-at-least-I-do-not-yield-to-Turkish-music" virtuosos singing minores.
Btw my No1 favourite chanter is Chrysanthos Theosodopoulos (+1988) of Thessaloniki:http://www.youtube.com/watch?v=U4g7I0Z5J5ghttp://www.youtube.com/watch?v=FLCYn_DA0yE
Close second comes the Master (Charilaos Taliadoros), listen to an 86-year old voice:http://www.youtube.com/watch?v=jf-nvi_uPZohttp://www.youtube.com/watch?v=R0eqOR2cnP0