In Config.txt, all the awareness section has changed altogether.
All awareness modifying effects now use absolute values instead of percent-based values. If you have any of those in your mod, you should adjust the numbers. The value determines the increase per day, so an effect of -2 will decrease the daily awareness growth rate by 2. See "meditation" research and "stealth" skill in the original configs as examples.
Awareness should no longer be used in formulas for determining base defense difficulties, since attacks only happen when awareness is at 100% now.
Full Release - backward compatibility breaking changes
Amount of experience per enemy is now defined per tier in Enemies.txt. If you add enemies that don't inherit any tier, you need to add these per enemy. If you add new tiers, you need to give them exp values.
Profession preferred tasks are now defined in the Professions.txt file instead of in Config.txt.
Removed difficulty milestone "difftier3extra" and added milestones for tiers 4 and 5.
Changed skill ID for scout (now spotter) and artisan (now tinkerer). Any links to those skills should be modified. Scout and Artisan are now professions.
Level up skills defined in Professions.txt now have a new mechanic. Instead of defining a few skills per level, you define which categories are available per prfoession, and then define the skills per rank of each category in SkillLists.txt.
Enemies.txt: Removed survivor4/5 base classes (they weren't supposed to be there in the first place)
Enemies.txt: Instead of defining min/max difficulty, enemies now have a "level" property that determines when they appear.
Enemies.txt: Instead of defining "difficultyval" property, enemies now have "amount" property that determines their value relative to their tier. Lower value means more of them will spawn.
Items.txt: Items have "level" property instead of min/max difficulty to determine when they spawn as loot and in traders.
Items.txt: Items now have new properties that affect when and how they appear in traders.
Research.txt: Research subjects now have a level property. This affects how we calculate the player's "current tier", which is currently used only to determine what items traders offer, but may be used for additional purposes in the future.
Config.txt / Texts.txt: Preset survivors' names are now localized. The previous syntax still works but we recommend moving their names to Texts.txt.
Config.txt: A lot of the difficulty settings have moved to a new file - Difficulty.txt. Much of the settings that determine how enemies are generated have changed in Syntax as well.
Config.txt: Definitions of difficulty levels per terrain now use a "formula format", so the previous ranges of "400-500" would evaluate to -100 instead of "random number between 400 and 500". Use "400 : 500" for ranges instead. We also support variables defined in Difficulty.txt now.