The plugin auto-upgrade functionality with 2.5+ is great, but it lacks some rollback features in case of a failed upgrade.
Currently, if the upgrade fails upon activation of the new version, then then you are left with a deactivated plugin (new version). Getting it back up and running requires finding the previous version and reinstalling it in wp.
It would be great if the following process happened during auto-upgrade:
1. When a plugin upgrade is executed, the existing version of the plugin / plugin directory should be moved to a new / temporary location.
2. If the plugin re-activation fails, it should immediately re-install and re-activate the previous version from the temp location.
3. The previous version should be stored indefinitely in case the blogger needs to roll back if something is wrong with the new version. (Single click rollback feature would be great).