Size is close to 50 MB. More info will be edited in when available.
npc_abilities.txt, npc_units.txt, and npc_heroes.txt have all been relocated inside of the game's VPK structure and will now require use of a tool such as GCFScape or ValveResourceViewer to inspect (previously, it was located in "dota 2 betagamedotascriptsnpc" in a steamapps folder wherever you have the game installed)
One side effect of this change will be better protection against corruption or deliberate tampering
When using the hero chat wheel with Pudge's The Toy Butcher persona equipped, Pudge will now say "Why can't we be friends?" as intended
A GC protobuf and a console command were added, the latter of which is named "dota_number_of_samples_for_lane_prediction", that appears to suggest that the GC will start to guess which lane a player selected when logging match statistics post-game (the default value is 8000 samples)
For developers/modders working with the Panorama UI system, AsyncWebRequest is now deprecated, "and will be removed in a later release!"
Although it looks like the inventory image for Spirit Breaker's Pillar of the Fractured Citadel set was updated, it is visually unchanged (it appears only the block type was switched from REDI to RED2, and a few .vtex_c flags were removed)