I've always thought Minecraft was an interesting programming challenge (I made a little clone of my own a while back (with portals, for whatever reason): http://www.youtube.com/watch?v=Qk_KjtbHUIs).
On modern graphics hardware, backface culling is done by the hardware itself. It would help if this demo were anywhere close to the limits of the hardware, which it isn't.
riyela is probably referring to the way Minecraft itself draws the world. If you have a solid block floating in free space, Minecraft draws all six faces of that block. However, if you have two solid blocks touching, Minecraft doesn't bother drawing the faces between them. It only draws the faces that are exposed to air (and are, therefore, visible), so it doesn't need to draw nearly as many faces.
That should get a decent performance improvement.
Slowly I learned how to acquire and build resources. I found an island and built a house on it. Monsters were no longer a threat. I made a farm and had all the wheat I needed.
I started caving not for survival, but to acquire extra resources. I turned those resources into large builds, both aesthetic and functional. I built a minecart track into my mine shaft just for the convenience. I built art on my island despite the fact that nobody else would see it. There was a huge amount of freedom.
Minecarts used to act very strangely, to boost them you'd put them side by side. I consulted the Wiki to figure this out, and learned about redstone at the same time. I started building larger-scale contraptions with it, and made a "challenge map" (I had never seen one before at this point).
Multiplayer came out around this time, and while extremely buggy, it allowed us to play survival with friends. This hit at the perfect moment because up till that point, I had a full understanding of the game and my interest was beginning to wane. Multiplayer rejuvenated my interest, and I worked on some large builds with friends. All vanilla, of course.
And now it's what, a year later? Minecraft has had some very large updates lately, and while I'm not as enthused as I once was, I'm still looking forward to see what the Mojang team and modders are able to do with the game.
1. It's an incredibly deep game about surviving, exploring, and reshaping the natural world.
2. It's an artistic medium that allows elaborate visions of architecture and fantasy worlds to be realized very easily, albeit with large blocks.
3. It's a fun way to hang out with people online, like Second Life without the indulgence and materialism.
4. There is whole field of "Minecraft science", where people do experiments to figure out how the game works and invent machines in-game that do things way beyond what the developers ever intended.
5. People design custom worlds and publish them for others to play. These can be long narrative adventures, short puzzles, parkour courses, and some team sports have recently emerged.
6. A huge developer ecosystem has grown from only decompiled and manually de-obfuscated source code. People have modified the game in amazing ways, and some mods have been incorporated into the official game. An official developer program is in the works.
7. "Let's Play Minecraft" shows on YouTube are unusually entertaining. The game is so open ended that you can really get creative with the format and content of the show.
I don't know what it will be for you, but I'd be amazed if you never got anything out of it.
Having that said, the fun of Minecraft (besides doing survival mode's challenges/killing monsters) is being awesome: take a peek into Minecraft top 5 creations for mindblowing spaceships, castles, roller costers and circuits!