What differentiates good from bad programmers? This article lists some valid criteria. Here's the short version

Positive indicators:

• Passionate about technology
• Programs as a hobby
• Will talk your ear off on a technical subject if encouraged
• Significant (and often numerous) personal side-projects over the years
• Learns new technologies on his/her own
• Opinionated about which technologies are better for various usages
• Very uncomfortable about the idea of working with a technology he doesn’t believe to be “right”
• Clearly smart, can have great conversations on a variety of topics
• Started programming long before university/work
• Has some hidden “icebergs”, large personal projects under the CV radar
• Knowledge of a large variety of unrelated technologies (may not be on CV)

Negative indicators:

• Programming is a day job
• Don’t really want to “talk shop”, even when encouraged to
• Learns new technologies in company-sponsored courses
• Happy to work with whatever technology you’ve picked, “all technologies are good”
• Doesn’t seem too smart
• Started programming at university
• All programming experience is on the CV
• Focused mainly on one or two technology stacks (e.g. everything to do with developing a java application), with no experience outside of it

Have a look at the whole thing. It's worth reading. I'm not sure which of the positives are the most important. I probably would choose "Learns new technology on his/her own" and "Passionate about technology". If these two are not there and if I see strong indication of "Programming is just a day job" I would probably not hire that person.

An interesting experiment is to think about your colleagues and yourself and apply these indicators. Are you a good software developer or a bad one? What about your colleagues?

We're not hiring at the moment, but when we start searching for new development staff in the future I will definitely come back to this list and see which indicators I can find when interviewing candidates.