Overall a nice product that offers something I feel WoTC neglected. There are some very minor formatting issue that don't hinder readability but do cut down on presentation: spell names should be italicized and Orcus' second ability isn't properly spaced. Besides these small issues I think the overall flavor of each Demon Lord has been captured well by the abilities offered to each subrace. I believe that Crown of Madness might be a better fit for Demogorgon's level 5 spell, as it captures the chaotic and mad nature of him better, but that's personal preferance. Similarly, Graz'zt's level 5 spell might be changed to Suggestion, to avoid undue duplication.
I recommend picking this up if you're interested in offering more tiefling options for your players (or yourself) that fit well within the base game.
[5 of 5 Stars!]