This new page can be customized can be fully customized to fit both branding and design, and contain exactly the information you want. The default maintenance page contains links to documentation and authentication for the final upgrade step.
Hiding the Maintenance Page
Additionally t is also possible to continue showing your website while Umbraco is in Upgrade mode. This will allow website visitors to continue browsing the site while the upgrade is pending. This is done with a new configuration option.
Hiding the maintenance page should be used with caution though. It is not recommended to let Umbraco be in Upgrade mode for extended periods, so this is a feature you can use for specific use cases, and you should remember to go to the backoffice and finalize the upgrade.
More information along with a tutorial on how to customize the maintenance page can be found in the documentation.
Single Block Mode in Block List Editor
The Block List Editor now features a Single Block Mode. This is useful when the editor is used for e.g. settings or configuration on a site and contains a single block that should always be present.
It essentially provides an alternative to Groups and Tabs by allowing you to hide (or collapse) the properties on the block and comes with all the other benefits of the Block List Editor such as custom labels, Settings, Property Actions, and more.