Let multiple tabs scroll continuously together. Two side by side let you see more code in context on a widescreen monitor. (Or have multiple, not limited to two).
Works great with CodeGlance for a Sublime style preview pane in the right gutter.
TODO - lots more.
This is Alpha, so may be buggy. Report any issues here: https://github.com/jawspeak/intellij-joined-tab-scrolling/issues.