I tried to get into Minecraft on my Christmas holiday, mostly because I had heard good things, I saw many impressive fortresses built and thought I might like to give it a go too. Because I wasn't ready to commit just yet, however, I opted to try the old 0.3 version in-browser. It's not quite like the current version, of course, lacking even the resource-gathering aspect, but it was adequate to show me whether I had enough spatial imagination to build things in the game.
I wandered around adding soil cubes to make land bridges for a bit, and I hollowed out a stone cliff into a boring square grey room. I dug down to get to bedrock, fell in some lava and got stuck. It seems that "death" was also not part of the 0.3 version, but neither was jumping out of lava again. So I had to restart, losing everything I'd done, which I admit is not what would have happened had I bought the full game.
Next I laid a foundation for a small castle and built up some short walls and ramparts, with an underground entrance. It looked like rubbish, and making it felt really awkward from a first-person perspective. The last thing I did was build an arbitrary tower as high as I could. I fell off many times, got bored and logged off for good.
This might not be your experience with Minecraft, and it certainly shouldn't be taken even as a review of the full game. All I mean to say here is that, as a demo, version 0.3 is entirely inadequate and did not inspire me to buy the full game, even though I have been thinking about it for over a month now. Maybe it will encourage you to buy the full game, but for me it did the exact opposite.
Mokalus of Borg
PS - It's still possible I would enjoy the full game.
PPS - But I still have other games to play before I try that.