TL;DR 2 new enemies and small areas, no new bosses. also, your saves aren't compatible with the new update. To be regular about this, I started using semantic versioning.

Bugfixes:
+ HP/energy don't reset on save anymore
+ remapped controls persist across sessions
- removed surf. I might have left it somewhere else in the world, but I can't for the life of me remember where :^)
+ updated sensitivity for Orca Flip, Meteor Dive and platform drop to be achievable on gamepad
+ removed flickering gaps between world tiles at high resolutions
+ improved performance in the Deeps
+ fixed Deeps dialogue where Val's name should have been X-404
+ the energy door after the Lady of the Lake fight stays disabled when you reload the level
+ you can now jump if you're holding down and not on a platform
+ added an invisible ceiling on the Rena fight
+ fixed unlock persistence issues when starting a new game
+ fixed item persistence issues between scenes

New Content:
+ added a new area, Sewers
+ added new enemies
+ added a new area, Central Column Residential District
+ added a very small easter egg dialogue line if you figure out how to start hoarding Mercuryblasts in the Night Market
~ reworked the Night Market
+ added a way to get into Lauren's basement from below her house

Gameplay Changes:
+ increased bounce block hitbox size, they're easier to bounce off now
+ lengthened divekick hitbox active frames
+ you still only have one airdash, however there is now a 0.1 second window after leaving the ground where an airdash will count as a grounded dash
+ biker race is easier
+ Richter is slightly more aggressive

Visual Changes:
~ tweaked Val's portrait
~ added a splash screen pointing here, because random websites keep stealing and rehosting the files
~ new Night Market tiles
+ some doors now display an experimental text prompt that shows you where they lead
+ added build number UI

Internal refactors:
~ optimized Sludge Wastes area by tweaking enemy AI to not constantly poll for player position if they're far
~ used xNode scene graphs instead of scripts on game objects referencing each other
~ stopped carrying the same Player object between scenes, instead used ScriptableObjects to hold runtime data (you should see no different behavior, but your saves WILL be invalid due to a differing inventory storage format)
+ started using semantic versioning in case I need to do patches or anything
+ player controller compares fall distance for hard landing, not velocity