In the RC release thread, the following discussion arose:
http://drupal.org/drupal-4.6.0-rc#comment-31276
I had a minor problem with a feature disappearing on me - in this case, the Categories block. While the fix was relatively easy, I can imagine this kind of issue happening on some other sites where the feature removed might be a bit more complex with a fix that's not so obvious.
There were three problems, in my opinion, with how this change was handled:
1) There was no indication on the site that this feature was being removed.
2) There was no suggested alternative on the site.
3) (less of an issue) There was no period to allow users to phase out or replace the feature.
Drupal is a moving target and its back end and front end are always improving and changing. What I don't want to encourage is stagnation of either old, unused features or a bad architecture. However, there needs to be a graceful way to help users make the transition from one Drupal version to another. If we don't do this, users will soon be afraid to upgrade Drupal, and then the community will have to deal with the issue of having a dozen unsupported versions of the software that people are continually asking for help about or requesting features for.
While I posted a number of (poor) suggestions in the thread above, I might suggest instead:
For every single CVS change log made, a reference to an issue must be made.