The worst programmers I've met are the ones who are heads down and program. They are usually very arrogant and think they are gods. Case in point, there's a guy I currently work with who is a disaster. People are in awe of him because he will work until 4am and has improved the performance of our application 100-fold.
The problem is that during the design phase, he completely disregarded all of our design recommendations and did things his way. It turned into a complete disaster, with nothing working as it should, deadlocks and complete lack of scalability, etc. So yes, he worked until 4am to improve things and did improve the performance from the initial disastrous numbers, but it was all his own fault! As well, because he was so arrogant and stubborn, he ended up producing something that no one wants anymore because the interface is too abstract and hard to use. Now, our the product is being shut down before it has even launched, because we couldn't convince any consumers to "wait until the next release" to get it to do what they actually want. All the fellow programmers think he's an asshole, but all of the managers who don't understand what he does will undoubtedly promote him.
The best programmers are the ones who keep it simple, design things excellently and program it once, with maybe a couple of iterations of performance enhancement. I've met plenty of brilliant programmers in my time, and these are the key traits that they exhibit. The "brilliant", nerdy programmers that heads-down program are rarely any better than a smart, easy-going programmer that both works hard and spends more time listening to their customers and making common sense design decisions.
