I watched an hour or so of Let's Plays just now. Factorio really made me reminisce about playing Tekkit, especially the Red Power mods from Eloraam (man, I miss those), plus ComputerCraft, BuildCraft and not to mention IndustrialCraft2. It's the only reason I bothered to learn Lua and FORTH lol. However my thinking now is that programming probably gives me just about the same level of fulfillment and challenges, sooo I think I'll stick to that. Factorio does look very fun though!