A Chrome Packaged App version with file autosave would be great.

Ability to select two shapes and perform a boolean operation on them, such as subtract and union.

An automated way to export a package that contains all the font files needed for a proper web reading in all browser (.oet, .svg, .ttf, .woff), additionally include a css file with css code for implementation and a sample html file (similar to what you get when create a webfont on http://www.fontsquirrel.com/tools/webfont-generator)

Add an interactive trainer, like http://type.method.ac http://shape.method.ac http://bezier.method.ac

Any other file types to consider?

While you are editing a certain character, specify some other characters to show to the left or right of it, so you can see how that character looks in context. Maybe also edit kerning values as well.

An automated process to create accented versions of characters

Right now there is only Undo!

Improve the live preview experience: Tear it out to a new window, support paragraph-level previews, automatic word wrapping for sample text...

Currently handles can be locked vertically or horizontally. This would enable you to lock a handle to any arbitrary angle.

An automated process to take all the characters in a font and slant them at a specified angle.

Fonts don't support paths with stroke thickness, only fill. But, we could allow you to specify a path with stroke thickness, then when exporting a font, that path's stroke could be outlined to create a filled shape.

A new Path Point action that would set the handles either vertically or horizontally, and lock them to that orientation. Useful for the extreme left/right/top/bottom points of curved shapes.