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: 
From [the wiki](http://www.minecraftwiki.net/wiki/Classic#Advantages_of_purchasing) about the classic version:

> 
> Advantages of purchasing
> 
> 
> Although this mode is free to the public, there are several advantages
>  made available to those who have purchased the game. Some of them are
>  the ability to:  
> 
>  - Use custom skins in both singleplayer and multiplayer.  
> 
>  - Use mods that require placement of files in the original minecraft.jar folder.  
> 
>  - **Build with more blocks and items.**  
> 
>  - Use crafting and create items.  
> 
>  - Combat mobs. 
> 
> 
> 

From a purely creative point of view, you will get more space, and more blocks to choose from, in the full version.

Keep in mind also that Minecraft classic is a prototype which has not been updated since 2009. From a technical point of view, the new version (full) will perform better, and look better (new lighting system).
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.