> By locking down the version you don't increase stability, you just lock in the current instability.

Locking down versions brings stability to the user experience: on a system-wide scale, known and static issues are better than unknown and ever-changing issues, obviously.

> Well maintained software gets better with time, bugs get fixed, security holes get fixed, the developer tests, then decides when there software is stable and then releases it.

This is simply false. There are bugfix releases and feature releases, unless you are implying that your definition of "well maintained" allows for bugfixes only.