Post feedback here for version 48/49, any bugs you encounter, etc.
We know bubbles/soap is funky and "Newtonian gravity" appears to have no affect, that will be coming to a beta near you soon.
Things to check out:
Simulation options (Replaces the legacy, or 'heat simulation' button)
Conversation notifications in-game
Decorations (Press b on the keyboard, the decorations do not save currently)

New in 48.2:
New BHOL and WHOL, the old ones are renamed VENT and VACU. The new ones use the 'Newtonian gravity' , it must be turned on in the options menu.
Conversation notification fixes.

New in 49.0:
Speed improvements for liquids, quartz and others.
Decorations now ONLY can be drawn on particles, and follow them.
Gravity and decorations are now saved.

New in 49.1:
Lua bindings and console (Documentation: https://powdertoy.co.uk/Wiki.html?id=lua (unfinished))

New in 49.3:
Improved thumbnail scaling
Better support for favourites (the ability to remove them)

New in 49.4:
Even more improved thumbnail scaling
Fix setting some particle properties with the console (x, y, temp)

New in 50.0:
Support for legacy console commands (prepend with a "!" e.g "!set type all watr")
Mercury, very heavy liquid (heavier than some powders) expands and contracts based on temperature and conducts electricity.

New in 50.1:
Fixes for SOAP bubbles and STKM.

New in 50.3:

• Attempts to fix some crashes and other issues
• Air temperatures now follows air velocity (sort of buggy)
• Gravity wall, exclude certain areas from influence of gravity
• Available for Mac OS X

Download here: https://powdertoy.co.uk/Download.html

@shroom207 (View Post)
Deuterium sensitivity is now relative to it's 'life'; white deuterium will almost instantly trigger a detonation whereas normal deuterium will behave as before, this makes smaller deuterium bombs possible.

@boxmein (View Post)
It's not quite in-game convos, just a notification. It may be extended in the future .