good but a little complicated
great tutorial, that explains drawing in perspective perfectly, but perhaps too perfectly.
I would say that it's not always necessary to draw so many lines because sometimes I find that you can get so wrapped up in the math and technical side of it that you forget to simply USE YOUR EYES.
Perspective drawing can be a big help, but just remember not to get too serious with it, rely on your eyes just as much as your brain, and you may save yourself a lot of tedious line drawing.