The practice of only supporting latest WP version seems popular in WP development circles, yet there is massive percentage of blogs running outdated versions. Not supporting those plugins seems it can lead to significantly less usage than if (some) older versions are supported.
Support of older version comes with major issues, especially:
- Complicated testing for multiple versions (unit tests?);
- No access to latest functionality or having to backport it;
- Incompatibilities of your code between WP versions (works in one, breaks another);
- Wider hosting requirements range (older PHP and MySQL versions, dropped by WP).
In your experienced had you ever had to support older WP versions in your code?
Which organizational and technical practices had produced good results?
What type of code do you use to manage the multiple version support.