Can I confirm knife actions with the mouse, or some other key than Enter? Going all the way to Enter breaks the flow in a way that's inconsistent with blender's philosophy.
This is mapped by default to Enter, NumpadEnter and Space but you can change it if you want to.
To change it, you go to User Preferences > Input.
- In the search field, type Knife and it will bring up the relevant panels
- Toggle Knife Topology Tool
- Toggle, Knife Tool Modal Map
- Change any of the Confirm options to whatever input you want by clicking in the input field to the right and then pressing the key you want to use OR
- * You can add another one with Add new at the bottom.
Go into your User Preferences menu, go to the input screen and you will see a drop down menu arrow called knife model tool map, open it up. Go to the arrow which says 'Any number pad enter', this will be on the right side and then click your middle mouse button. The confirm of ending your knife cut will now be assigned to your middle mouse button.