If I'm repeating something that has already been said, consider it an up vote.
- Well laid out, user configurable menu system. Including context menus.
- Well laid out, user configurable toolbarS, as in multiple
- Overall UI consistency with strict adherence to the standards of the operating environment
- Macro facility - enable users to create macros that are assignable to toolbar buttons and hotkeys
- The ability to apply templates to tracks that already contain media items
- Make 'None' = 'None' instead of 'None' = 'Anything/Everything'
- Make tracks generic and capable of being any kind of track, bus or folder
- Provide a purpose built Monitor FX bin that is ignored during mixdown
- Provide a rock-solid, easy to use, per track MIDI mapping capability
- Provide a simplified, flexible, easy to use interface for setting up/configuring MIDI controllers
- Provide a monthly update system for delivering fixes/enhancements with full rollback capability
- Respect and maintain user preferences during updates
- Implement a MIDI step recorder that operates using arbitrary patterns of note values, including rests
Some of these are available in some DAWs, some aren't available at all in the 3 I'm most familiar with.
I'll add more later if I think of something else.