I separate Minecraft and Modded Minecraft in Ages (after Beta) in terms of Game Design (I will try to separate based on Technology later on):
Beta 1.0 to Beta 1.4: First Minecraft Age: people often played vanilla and toyed around with redstone, which was fun - we had redstone computers back then, no fancy CC things or RP2. Also some mods that weren't really fancy (pistons).
Beta 1.5 to Beta 1.7.3: Second Minecraft Age, First Modded Minecraft Age: we had IC, TC1, BC... They all were the first "great" mods. It was something new, with features people hadn't seen yet. It was something that started separating the community.
Beta 1.8 to 1.0: Second Modded Minecraft Age: The mods were rebooted - IC2, BC2, TC2 and EE2 were born, and so was Forestry (which was turning into a powerful addon), CC and Railcraft, RP2 was starting to take shape.
1.0 to 1.2.5: Third Modded Minecraft Age: Maturation of the reboots. Most mods were interestingly growing, and you could automate essentially ANYTHING. RP2 was an almost essential mod, and BC released BC3! That was impressive back then.
Beta 1.8 to 1.2.5: Third Minecraft Age: Hunger - fighting enemies was an engaging experience. People were focused on "what can I do now", since the game of diggy holes was ending sooner. From railways to arenas, everything had a function because mining wasn't as interesting as it once was.
1.3 to 1.7 (possibly): Fourth Minecraft Age: Exploration, exploration, exploration. Almost everything is based on "what is out there in the world that I haven't seen yet". Horses, new dungeons, witches, new ores... 1.5 was the odd one out, and it went to allow less exploration-based players to do something new and interesting.
1.4.6 to 1.5.2: Fourth Modded Minecraft Age: REBOOTS PART 3! TC3, EE3, Forestry 2.0, boilers, touchscreens, Tinker's Construct and Natura, SC2... This was interesting because mods were branching to everywhere and started covering eachother's functions - we could choose something different every time, there was no need for "just this mod".
1.6 to...: Fifth Modded Minecraft Age: Reboots and nerfs. It seems people are slowly running out of ideas now, to be honest.