The purpose of this post is not to give you a complete rundown of the new playtest rules. I assume they were printed with a limited run and not released in PDF for a reason, so I'm going to respect this and only call out a few things here and there. This is also not a review or analysis of the playtest document.
The purpose here is to provide some suggestions and resources for using these rules.
First, I made a "no frills" character sheet. This uses core LotFP rules + new playtest rules. I stripped away all my house rules, and left large "notes" sections for things we need to track as we go:
Next, you should buy Wonder and Wickedness. Perhaps the biggest change in the playtest rules is how magic is used. The magic system is very similar to what is presented in Wonder and Wickedness, and it will make your life easier if you just pick up this book and use the spells within rather than trying to convert all the LotFP spells over. I did a mix of both with my group, but more and more am just relying on W&W for the spells.
W&W is pretty awesome, and seems to be designed with LotFP in mind. On the other hand, there are some peculiarities. For example, the table of contents lists page numbers where you can find spells, but there are no page numbers in this book! The spells are organized by Specialities, not alphabetically (or by level, since there are no levels), making it difficult to find any spell quickly. Then, the spell catastrophes are in their own section rather than with the spell they're associated with, so you have to dig through more numberless pages to find them. Finally, to determine spells randomly, you have to roll a d56.
I hardly ever write in my books, but here's what I did to fix this:
First, I went through and numbered all the pages, making sure that everything matched up to the table of contents (it did) and then I added the page numbers for the catastrophes to the ToC, as well as the Spell Index, and put stars by the page where players need to go to roll randomly for spells.
Here is the spell selection page. Rather than roll a d56, players roll two d8s. The first determines the specialty, the second determines the specific spell. If the player rolls a 7 on the first d8, they instead roll a d50 for one of the magic items provided in the back of the book. Only the player who starts with this item can use it, so when they die, its power is lost.
The next change that you have to deal with is that Read Magic no longer exists. Instead, Magic-Users use an ancient, dead language to write their spells in their books. The idea here is that it makes it harder for other Magic-Users to decode them. The playtest document is sparse in terms of how this works mechanically in the game.
So, assuming the way languages are gained in the base game (roll a d6 plus your language skill +/- any modifiers) most people are going to be getting a -3 to their languages roll, which means it's unlikely you'll know the language already. So, it takes time to research the language first, and then decode the spell (the playtest rules do note that it takes time to figure out the spell even if you know the language due to the idiosyncrasies of how each M-U records their spells). I would say a successful "Know Languages" check cuts this research time in half? Or at least gives the reader some clues about what the spell is...
Anyway, I created a generator that includes actual ancient, dead languages for you to use. The instructions are in the document itself. The coolest thing is that the original source included subgroups and families, so you can give the player a bonus if their own dead language happens to share a family or subgroup with the language they're trying to decipher.
Finally, I want to call out a specific part of the rules because we found them confusing at first:
All weapons will now do 1d8 damage. However, Armor will count double against Minor and Small weapons, and half against Great Weapons and Polearms."
The semantics are a bit confusing here because in D&D everyone has an armor class, so the above seems to imply that you double armor class, which would make an unarmored person almost unhittable with a dagger (their AC would be 24). But LotFP tends to present things in terms of "unarmored" which is 12, and then Armor provides bonuses. Although, the armor doesn't actually provide bonuses, it provides a flat "AC" (like leather gives one an armor of 14).
We finally decided that the difference between the armor rating and unarmored is what is doubled or halved. So if the party is fighting a monster with an Armor of 18, the person attacking it with a dagger would hit on a 24 (18-12 = 6, 6*2 = 12, 12+12 =24). The person attacking it with a Polearm would hit on a 15 (18-12 = 6, 6/2=3, 12+3=15). I'm not a fan of doing this calculating as a Referee whenever the players are fighting something, although Raggi does indicate these calculations will be on the character sheet if they are used in the final version.
Also, I wasn't sure how to handle monsters attacking players in this regard, but Raggi clarified online that monsters just use the traditional rules (or whatever is indicated in the book the monster is in). So they would use various damage dice, ignore the halving and doubling rules, etc.
Let me know if you have questions or if there are other resources you'd find useful to run LotFP using the new Playtest Rules. I love researching and making stuff!