Usually I don;t mind back row seats since most shows I go to I have seen already, so I am just going more to hear new voices and such, and have sat in the back of the mez for Lion King and it was really far back.
The thing about Lion King in particular (my opinion anyways)is that since tie costume/puppets are so important, if you are not close enough to appreciate the intricacies of them, then the show can get a bit, um, boreing (and this is from a huge fan of the show). This is something that can happen alot too when you have shows with minimal set design as far too often in Lion King the stage is empty and if you are sitting up at the back you feel like you are staring at a big old brown empty stage.
http://www.flickr.com/photos/27199361@N08/ Phantom at the Royal Empire Theatre