Cant speak of obstructions for Poppins (i havent seen it) but Lion King was fine, although everything is far away.
I didnt find it to be that steep, London theatres are far worse, the balcony of the Palace in london is more than 45 degrees.
if you are in the new am's balcony, just try to be in the centre othewise you'll be seeing almost more of backstage than onstage
http://www.flickr.com/photos/27199361@N08/ Phantom at the Royal Empire Theatre