Minecraft is fun. However I'd clearly state that Minecraft, especially the early multi-player stuff that Notch worked on, /was/ a disaster.

Only now, three numbering schemes later (alpha, beta, release), in release version 1.8, does the core game actually have features such as abstracting implementation IDs from object types (EG: now there is minecraft:glass to resolve instead of remembering decimal value 20. Though mods for r1.8 are only just beginning, so that scoping might not yet exist.)