While holding an item and right-clicking a container, you can now hold Alt to only take from the container, rather than first attempting to transfer to the container. Useful, for example, when you want to light a branch on a fireplace without first filling the fireplace up with fuel (e.g. branches).
Very stupid fix that breaks good user experience. Most custom clients allow to fill the container with items from player's inventory until either the container is full or no legit items left in inventory. It was most used to
fill the containers - e.g. fill steel crucibles or food throughs or compost bins. Need I say that it all involved a simple alt+shift+rclick combo? Now this useful, everyday-use and well-known feature is broken in favor of some rare niche action.
Of course, in some days there will be a fix for this in most clients. Of course, most players will eventually adapt (it would be painful though - re-learn the action you get used to for several years). But could you do some research at least and consult players BEFORE you implement such changes?
I would even suggest using some popular custom clients to learn how this game is played - but that obviously would be in vain...