This seems to be (should be) a FAQ. There is an ACM article about beautiful code recently. There seems to be a lot of emphasis on easy to read/understand. I'd qualifier this with "easy to read/understand by domain experts". Really good programmers tend to use the best algorithms (instead of naive easy to understand O(n^2) algorithms) for any given problems, which could be hard to follow, if you're not familiar with the algorithm, even if the good programmer gives a reference to the algorithm.
Nobody is perfect including good programmers but their code tend to strive for:
- Correctness and efficiency with proven algorithms (instead of naive and adhoc hacks)
- Clarity (comment for intent with reference to non-trivial algorithms)
- Completeness to cover the basics (coding convention, versioning, documentation, unit tests etc.)
- Succinctness (DRY)
- Robustness (resilient to arbitrary input and disruption of change requests)
