The INSTALL.txt file that is included in Drupal core is outdated, very long and contains many details that, in my opinion, are not very relevant to the installation process.
This information could better be stored on line on drupal.org than inside Drupal core:
- docs on drupal.org are easier to maintain
- more up-to-date and better written Installation instructions already exist on d.o. http://drupal.org/documentation/install
- d.o. docs can easier link to information that is interesting but not immediatley relevant to the installation (currently INSTALL.txt includes such topics as cron configuration, multisite installation, "what is a module", building and customizing your site)
- drupal core becomes, yet, a little bit, easier to maintain
- on d.o. it is easier to keep a consistent style and make larger document changes
The INSTALL.txt file could include a short installation overview with one or several links to d.o
One could argue that you need off line installation instructions but is it still realistic in this day and age that one installs a web content management system without internet connection? Furthermore the INSTALL.txt is littered with links, so the current version is not as off line as it seems.