This is legitimately the worst 5e supplement I've ever seen in my life, and the fact that it's performed as well as it has depresses me. The bottom line is that this is a very bad product you should never buy, but I'll break down its many failings into a numbered list.

1. Reason for existing. Strahd does not need to be CR 27. He just doesn't. He doesn't need 29 AC, he doesn't need resistance to all damage, he doesn't need to make 9 attacks per turn (4 base, 3 legendary actions, monstrous form, and haste), and he especially does not need to be more powerful than archdevils and demon lords. The regular Strahd, used intelligently, in Castle Ravenloft, with minions, will wipe the floor with your players plenty. You don't need this product.

2. Fun. Your players will not have fun fighting this statblock. They will not enjoy missing every attack because he has 29 AC. They will not enjoy whittling through his effective ~350 hit points, with 30 hp of regeneration a turn. They will not enjoy you permanently cutting their arm off as a legendary action. They will not enjoy being permanently stunned with no roll by a DC 22 Power Word Stun. They just won't. Moreover, you will not enjoy running this statblock. If you thought regular Strahd was too complicated to use effectively, wait until you get a load of the A4 page and a half of statblock that this monstrosity is, complete with impossible-to-parse walls of text, an additional half a page of magic items you have to understand, and a full page of completely opaque and complicated spells you have to learn how to use.

3. Proof reading, spelling, grammar, punctuation, and math. The whole product is riddled with capitals where they shouldn't be, lowercase letters where they should be, spaces after commas, no spaces before commas, mispelling names (Mordenkainen is mispelled in two different ways in one paragraph, and not capitalised either time) (also Strahd is repeatedly spelled "Strand", and often also not capitalised) and just terrible, terrible spelling and grammar. Quote: "As the lord of the land, Its totaly unacceptable for strahd to not have magic items equiped when he fights to kill his en-emies." The math is also atrocious. Strahd does not have a proficiency bonus listed, and his attacks, saves, passive perception, and spells all appear to use different proficiency bonuses.

TL;DR: Product bad, do not buy.

On the one hand, I really appreciate the enthusiasm and effort put into this upgrade to Curse of Strahd's take on Strahd, which was disappointing. There are a lot of interesting new features in here and this would certainly make for an epic final boss battle. For bonus points, they also provide/convert four additional spells.

On the other hand, this product overdoes it a bit. There's so many options here that it could be a chore to run this version of Strahd, since you might be overwhelmed with choices. Also, was it really necessary to make Strahd more powerful than demon lords like Orcus or Demogorgon? The formatting issues don't help this product either (although the new mechanics seem OK aside from that).

This version of Strahd is way more fun to run than the little wimp included in the module. I am pretty sure the paladin in my group would have taken the Wizards version of Strahd out in single combat. But this version! This version had 3 of my 6 party members making death saves by the end of the combat. They took him out, but they had to give everyting to do it.

Great stuff, would just hope for some editing to have taken place at some point. In the day and age of auto correct and grammatical suggestions, there are far too many errors in an otherwise great document. Another small complaint is the Baleful Attractor new spell. Seems overly complicated and/or vague in its application. 15 foot diameter, but it has a target not an area or point of effect? Does it follow the target or stay at the point of effect? And does it really last for 10 minutes? All target spells are redirected for 10 minutes (concentration dependent)? Does it stay for 10 minutes and end when triggered or just simply continue to remain? Seems a bit unbalanced or not clearly defined enough imo. Great work otherwise albeit my nit-picky suggestions.

I love this! I was getting nervous about my party absoluting trouncing the CR 15 Strahd included in the book, and this has definitely alleviated my worries. I don't feel rushed to initiate the final combat before my party is too strong and they make a joke of the confrontation.

Great new-image on Strahd. I appreciated a lot the fact of reducing the CR depending on the players action/information and so on. I would love to have some more lore on some things (perhaps what and why those items are there) but thats also DMs work!

Really nice since my players survived so far (level 6-7 party) will also help to extend the the campaign and gave me some new ideas on different twists :)! :D

Keep up the good work sir, that was really nice, well though and nicely written. I hope we see more of you. Cheers

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.