late april i think? i had known about MC for a while. watched lots of creation videos on youtube and was truly amazed. i put off buying it because i was worried my laptop couldn't handle it (it sort of does... depends on the map i guess). then i stumbled upon the yogscast. i was hooked on their videos. one day i found out about the free to play version and tried it out. it played well enough, i was drunk, and i bought it. i don't regret it in the least, but i'm waiting for the day i can afford a new computer so i can play SSP without it lagging on truly epic maps
I bought it pre-alpha. Before infdev in fact. Oh no, wait, back even farther... before indev. As a matter of fact, I bought it before there was any survival mode at all, just creative mode (or "Minecraft Classic" as you youngsters know it). Let's see, it must have been... late July 2009? Yep, shortly after version 0.0.23a.