I've had real issues with Inkscape, especially its user interface. It's just not a Mac app. I'd love to see someone tear the gubbins out of Inkscape and place them in a good user interface. (To be fair I have real issues with Illustrator's UI, too. And the App I choose to use isn't a Mac app to the point of being a Windows App on a PC in Parallels.)

Expression Design has a very simple, powerful interface: scroll is zoom, space bar is pan, unmodified click is select. I'd like to see someone make an SVG editor with a cross between it and Bret Victor's Gestural Zoom And Pan.

http://worrydream.com/#!/GesturalZoomAndPan