These are the official 9.15.1 patchnotes, quote:

“Introduction of ActionScript 3

We are moving to Action Script 3. This is good for the game because it will open up more ways for user interface performance optimization in the future releases, as well as make the workflow for mod creators consistent. However, in the short term, this change can have*an impact on the modding community, as the creators*will need*to update their mods to work with Action Script 3. We have worked with the modmakers to check compatibility for*the*biggest and most popular mods and have been able to verify 9.15.1 compatibility with a number of them. For more information, please refer to our dedicated article.*
Important: If you experience any technical problems with this update while playing with any mods installed, please uninstall those mods and try playing the game clean.*Please remember that Wargaming is not responsible for any compatibility issues stemming from using third party modifications. In case of problems with the*mods,*pleasecontact the author of the mod in question. *While we love our mod community, our Customer Service*cannot provide support for third-party add-ons.

Sound Improvements

The new system for sounds, that was introduced with Update 9.14, has been supplemented with*additional sounds, in order to improve the ambiance and the immersion, and in order to provide more detailed acoustic information about the battle to the player.
New Minimap Prototypes

With this version, certain maps will feature a new minimap design that is aimed at improving the player’s ability to assess and process*battlefield information. Based on player feedback, these new minimap prototypes may be improved and expanded to other maps with future game updates.
Replacement of the Lorraine 40 t with*the Bat.-Chatillon 25 t AP

The current Tier IX French medium tank in the autoloader line will be replaced by another vehicle, whose*characteristics*make it a more natural progression link in the respective tech chain.

Personal Reserves Available for Purchase In-Game

Personal Reserves can now be purchased with gold in their management menu in-game.
HD Models

Update 9.15.1 upgrades an additional 24 vehicles to HD quality and fixes the models of 4 tanks that have been visually upgraded in the past:

  • USSR: AT-1, MT-25, SU-100Y, SU-101M
  • Germany: Hetzer, GW Tiger P, Dicker Max, Grosstraktor Krupp, GW Panther, Waffentrager auf IV, E 75, GW E 100
  • France: AMX 13 57
  • USA: M22 Locust, M37, M8A1, T57 Heavy
  • UK: FV215B (183)
  • China: T-34-1, 121, 113″

How’s going this patch so for you so far?