Sir Michael furthers his comments on ancient magic, and is kind enough to consider many of the various responses (including yours truly): http://www.magickofthought.com/2012/04/why-study-ancient-magick-part-2/
I stick with my initial sentiments. The established egrigores help novices, and the ancient magic that worked then should work now. Of course, ancient magic that didn’t work then still won’t work now, and I think what he is getting at is that we should be better now at separating what works from the fluff.
But sometimes the fluff is like adding sugar to your coffee: it makes it more palatable to people who are still developing a taste for it. And sometimes people just like it that way – I’m good at chaoist sigil magic, but love the aesthetics of ceremonial ritual shouted in Hebrew. And patterning my devotional work after ancient Roman practices feels a lot more satisfying.
It really comes down to flavor and preference. We don’t need ancient magic, but sometimes we want it on an emotional level, and if it works, it works.