If enabled, the OS X feature Auto Save will automatically save your Sketch file regularly so it can be accessed, and reverted via Versions.
The pixel fitting options will round layers and points to the nearest whole pixel. Subsequent preferences will enable you to have this behaviour when resizing or aligning layers to ensure objects don’t sit on fractional pixels.
Should PDF and EPS files by imported as flat ‘images’, or should Sketch try to interpret the path data inside them and make the shapes editable?
Should Sketch Mirror always update to show whatever Artboard you have selected on the Mac or should it operate independently?