Question: I want to buy the full version of Minecraft, but I'm one of those creative types. What are some of the differences in Creative mode in the full version of Minecraft?

Answer: 
You can play the free version, so I won't waste too many words about it. You have a small sandbox and a few kinds of blocks you can mess around and build with. You can explore the randomly generated world for caves, pockets of air, etc.; you can grief with water sources... It's the core of Minecraft.

The paid version features a world many times as large, with blocks that do actually something rather than just sitting there (with the exception of the sponge, the only "useful" block in the "free" version of Minecraft and is completely useless in the paid version\*).

There's also adventure mode, which lets people play through your map without their ability to modify it in ways that break it.

\*As of version 1.8, sponges soak up water in a 5x5 radius, similar to Miencraft Classic
There is only about a dozen blocks in Classic, and they don't really do much. The full version of Minecraft not only includes nearly 150 blocks, but also has Redstone (an extremely flexible system you can use to make machines in Minecraft), custom avatars, infinite worlds, enhanced multiplayer, and the awesome survival mode. You can give it a try using the [demo mode](http://minecraft.net/demo), which lets you try a survival map for five in-game days.