Midi editor - display note names on the notes. So a C3 will have a small C3 written on it, similar to Cubase/Ableton/Reaper. Makes multi-voice harmony easier in the late hours. :)
Midi editor - ability to customize tool functionality like Sonar 8.5 (regardless of how efficient people claim the smart tool is, you can do far quicker editing in 8.5 once you customize the tools).
Staff view general improvements - like separate snap and note entry values, control over multiple voice handling, better note placement on the staff etc. Nothing that would take weeks to code, just simple upgrades that would help many users.
Spend as much time alpha/beta testing as possible and make sure the tests are accurate. The amount of bugs in X1 was beyond a joke, and beyond recent releases of PT/Cubase, both of which have a far larger audience to cover (PT HD, cross platform etc).