Top-notch tutorial.
This is easily the very best platform game tutorial I've seen here on Newgrounds. I've seen a lot of the weaker tutorials, but I've been able to figure out better ways of designing a platforming engine than they could provide.
I haven't made any games yet, but I just finished my platforming engine a couple of days ago. My code is similar to this tutorial's, except that the code for jumping physics in this tutorial is superior.
There are only a couple of things I didn't like about the techniques in this tutorial. I don't care much for putting platform code in the player. I like to put the code for platform behavior in an instance in the symbol for each platform. This way I can place several platforms without having to name each instance of them. Even so, your method works very well. Additionally, I don't really put any code in the player except for stop(). I put all the code for player behavior in an invisible controller object and name all of the animation frames for the sprite to be used as the player. That way I can interchange any sprite with labeled frames and name the instance "player", and I don't have to alter (or even copy and paste) code.
Despite my personal preferences, I'd say that this is by far the best platform game tutorial I've seen.