We adopted Debian after scanning all the distros available grading them with max. weightage on "Programming Convenience" and "maintainability". Debian "outperformed" all other distros with a great margin.
- Programming Convenience: With its abundant packages and its clever interface (apt) it's pretty easy to install a library or search for one. 90% of chances you'll get in the repository. Moreover all the cleverer tools of Programming (IDE, libraries, modules, modes etc.) you'll get in the repository and moreso just an apt-get install <package-name> does it all for you, you are back to coding.
- Maintenance: Debian rocks at Package Management. No distro gets even closer to this. We've had nightmares going thru the "rpm" dependencies earlier.
All our server/client machines in the Department run on Debian.