The more experience I get in the industry, more and more I value great developers that know how to distinguish great from good code. And I am glad that I had a fantastic experience reading and working with the Linux kernel - most of the code I had seen at the time falls into the category of great code.
There are many aspects of a great developer that one can think of, but I'd like to focus here on code readability and maintainability. First, one quite important distinction, especially for those used to following strict "code guidelines". Code readability is not so much about where you place the brackets, or any style that can be verified by a static analysis tool. These are usually what don't really matter much in my opinion.
The real readability is about the art in writing your code, not its science. Things like how to properly break your code into methods, how to name variables, classes, and methods, how to use spaces properly, how to make proper use of the fixed-width characters or align/indent code.
In my opinion, great engineers know that the code must not just work, but it must be a work of art. Something that you and others can read in the future and maintain. It is NOT just about getting it work. A lot of code I read works, but they are not readable, not elegant, and oftentimes not efficient at all.
Digressing a bit, I miss systems where you actually need to get the max performance out of a system. That seemed to require better engineers than nowadays. Now, with web services and cloud computing, oftentimes one doesn't care much about performance as you can always get a faster box to run your code. After working for two cloud providers, I see that this can specially happen with those providing these cloud services. I wonder whether these engineers who just throw more CPU power or memory at a problem actually ever thought of the cost of running a service and that this is one of the things factored in that will make the difference between being profitable or not. Or, on a more philosophical side, if they really feel pride of the engineering in the code they write.
But back to coding guidelines, I really recommend that you read the article below (published in the ACM Queue magazine) if you want to get better at that. It has a few tables that you should print out and put it up on the wall where you can peek when writing your code.
Coding Guidelines: Finding the Art in the Science
Today I also came across a new O'Reilly book on the topic called "The Art of Readable Code", which seems to be quite interesting and probably delve into this topic in much greater detail.
The Art of Readable Code