There are a lot of cool additions to this version of Strahd. I can immediately see a lot of uses for many of the new abilities, and how they fit in with with the "legendary vampire" feel given to Strahd and Dracula in many forms of media.
CR27 feels like an odd number to settle on, but there are methods for the players to lower his CR, which open up new quest options DMs can give their players, which I really like (more milestones!). Some of the bonus and legendary actions seem a bit much, though any DM can use discrection on which things to include and which not to. I personally will be using a lot from this PDF but still tweaking a few things down to get them exactly where I want.
TL;DR: Worth the money, in my opinion.