It's been just over five years since development on the 0.4.x branch began (wow, time passes fast). I still have a copy of the 2012-01-22 release on my desktop and occasionally play it. In the time since then, Minetest-engine has come a long ways - both performance-wise and feature-wise. It also has two major forks in the form of Voxelands (based on 0.3.x) and Freeminer (0.4.x-bleedingedge).
Platforms
Versions of Minetest have appeared on Android. The first releases were unofficial, though the Minetest team now maintains an official version. Minetest can run on Windows (XP-10), MacOS(10.7+), *BSD, and Linux. A port to iOS is theoretically possible, but has not yet occurred.
Minetest-game: No real change
Minetest-game has not changed much between 2013 (when farming and diamonds were added) to 2017. Lua-based mob mods have not been merged into the game. Reportedly, a separate mobs API in the minetest-engine is planned. However, Minetest-game remains unfinished - the foundation for players to build their own game.
Core Engine Features
Basic animations are possible, though few blended animations exist. Entity attachment is still terrible for moving objects. Modders should simply change player model and attributes instead of attaching player model to entities.
Worlds are still 64 square kilometers. Round worlds are theoretically possible, but will require substantial modification to the engine.
LuaJIT support has been standard since 2014. For large servers, many database platforms are supported.
With changes made to Irrlicht upstream and changes made to Minetest-engine, gamepad support is now possible, though not mapped by default. Split-screen can theoretically be done by running two copies of minetest on one machine, one with gamepad enabled.
[hr]
There have - quite obviously - been many engine tweaks and improvements over the past year. Can you elaborate?