1) Selector Mode: TerminalCtrl now allows full keyboard navigation for selecting text in a special mode called "Selector Mode".
   At the moment, three types of selection are possible in this mode: text, rectangle, word.

2) Annotations:  This is a cool new feature. User or the hosted app can now add annotations to terminal texts (in both plain text and rich text (qtf) format).
   This can be done via user input (mouse, or keyboard in selector mode) or programatically (using a simple, proprietary protocol). AFAIK, this has been one of the most favored iterm2 features.

3) Word Selection filters: Word selection filter can now be set by the client code. It allows cell-level inspection, so it is even possible to select blocks of text ("words") according to their SGR attributes, associated data type, or colors.

4) Highlighting: TerminalCtrl allows full cell-level highlighting.

5) Shell integration: TerminalCtrl now allows hosted apps or shells to notify the terminal of the working directory, so the terminal can be aware of its environment (and act accordingly).

6) Configurable Keyboard shortcuts: Keyboard shortcuts are now configurable and can be redefined in client code.