I heard of the older version from
Didn't like it, but a nice fully featured version on steam would definetly get my money.
it has defiantly changed since then there are monsters at night for a start, also there are more things to craft etc. The game is not for everyone a lot of people need a clearly defined structure to have fun. Minecraft is true sandbox game and has no defined goals. Everything you do is because you feel like doing it. But even if you don't like playing the game you can always just marvel at the insane things people have made, like the working computer and the model of the USS enterprise.
The guy who makes the game does plan to eventually make a full featured game with co-op survival, fort wars etc in the future. And is currently setting up a company so he can higher some people to help him develop the game.
Also I just checked the stats page http://www.minecraft.net/stats.jsp and 308,026 people have now bought the game (for ~10 EUR) so the game has now had a gross take of over 3 million EUR! holly crap.