I've played Medival Engineers.
It's actually an awesome little gem they are working on over there.
It is by no means an MMO/RPG like LiF, but rather an engineering, terrain, and physics sandbox. Think Gmod crossed with Minecraft, with a pinch of Phun/Algodoo.
Compared with LiF, there is an extremely heavy focus on
engineering your own creations, rather than simply throwing resources at preset objects and having them pop into existence.
For example, one of my own tinkering projects; a suspended-rail mine cart system with a 360* turntable at the end of the line. All of the components pictured (with exception to the suspension towers) were engineered and assembled by hand from individual timber sections.
Totally worth a buy if you have a beefy computer, and can deal with Early Access & the fact that survival mode and procedural terrain are not implemented.