The over all user interface has not changed much in Windows 3.1 from 3.0. The Program Manager now has a new "Startup" group that the user can drag program icons in to where they will launch on Windows startup. Windows 3.1 will no longer run in "Real-Mode", and requires a 286 or higher. It will not run Windows 1.x executables and Windows 2.x executables may not run properly.

Windows 3.1 now has built in support for for various types of audio devices.

Windows 3.1 also includes several screen savers. Ohhhhh, color...

I believe I read somewhere that these "Multimedia" enhancements and screen savers were available as separate commercial package for Windows 3.0.

Windows 3.1 introduces registry services. The registry in Windows 3.1 is used for storing file type information and OLE registration data.

Finally, Windows 3.1 also introduces a better way to add and remove Windows components than re-installing and deleting files manually.