A small feature that would make a huge difference for me would be the ability to customize the modifier keys (ctrl, shift, alt) used in conjunction with the mouse wheel for zooming and scrolling. Basically, every program that I regularly use follows this convention:

• mouse wheel = vertical scroll
• shift + mouse wheel = horizontal scroll
• ctrl + mouse wheel = zoom

These hotkeys are burned into my muscle memory thanks to Audacity, MuseScore, Mixcraft, Google Chrome, GIMP, Inkscape, LibreOffice, Kdenlive, and many other programs I use regularly. Whenever I use SONAR, I always end up trying to use the wrong modifier keys when scrolling and zooming, and it just becomes frustrating.

I assume you mean a horizontal zoom? Maybe an Alt + Mouse Wheel = vertical zoom? I wouldn't mind having the option to have the mouse wheel as part of the customizable keys. That way one could do whatever they wanted with it.

 
Have to like the way Melodyne handles scrolling!