[powatom]

I would say that a truly great programmer isn't necessarily technically amazing. For example, a vast knowledge of programming languages is something that anyone can learn with enough time and patience. However, it's the ability to problem solve: to look at what exists already and make something new out of it, that really makes a developer 'great'. It doesn't really matter if they know a language inside out when tackling a project - it's the ability to help themselves: use the language and any tools available / relevant to solve a problem in an innovative way.

It's kind of a hard thing to evaluate, I suppose. I would say that to 'become great' - you can't just sit around programming all day (although this will no doubt help). It's a kind of 'knack' for working problems out, finding new techniques, using tools in new ways etc. These are all the things that make 'great' programmers great imho, and none of them are actually directly related to programming. In my experience, people who are REALLY good at solving programming problems are REALLY good at it outside of the programming discipline too.