Installation Changes in the 2015 Release

Installation

32-bit support: Revit LT supports 32-bit computers. However, all other editions of the Revit software no longer support 32-bit computers, including Autodesk Revit, Revit Architecture, Revit MEP, and Revit Structure.
Revit content is now installed as a separate module during the installation process. Revit content packs include help files for offline access to the Revit help system. See Select Content for a Revit Installation and How Can I Use Offline Help for Revit?
Locally stored files for the Revit help system (for offline access) are now stored in this location: C:\Program Files\Autodesk\Revit Content 2015\Help
UniformatClassifications.txt and a newer version of the file, UniformatClassifications2010.txt, are now stored in this location: %ALLUSERSPROFILE%\Autodesk\<product and release>\Libraries\<locale and language>.
In previous releases, UniformatClassifications.txt was stored in this location: C:\ProgramData\Autodesk\<product and release>\UserDataCache.
If you put a copy of Keyboardshortcuts.xml in the UserDataCache folder, those custom keyboard shortcuts are copied to the user profile folder when a user first starts the software. See Important Files for a Revit Installation.
Software patches and updates are now managed using Autodesk Application Manager instead of Live Update.
Installation improvements for Autodesk software are described here: About New Features for the 2015 Installation Guide

Licensing improvements for Autodesk software are described here: About New Features in the 2015 Licensing Guide

Note: Revit LT does not support deployments.

To make custom keyboard shortcuts available to multiple users, add Keyboardshortcuts.xml to a deployment using the Additional Files feature. Using that feature, create appropriate folders and add the file to this location: C:\ProgramData\Autodesk\<product and release>\UserDataCache. See Additional Files for a Revit Deployment.
You can no longer include language packs as part of a Revit deployment. Instead, you create a separate deployment for each language pack. After deploying the Revit software to target computers, you can then deploy the Revit language packs. See Language Packs and Revit Deployments.
Deployment improvements for Autodesk software are described here: About New Features in the 2015 Network Administrator's Guide

Note: Revit LT does not Revit Server.