Inkscape and the Gimp are trusty tools in my daily tool box for various vector and bitmap image editing. Being open source applications, they have firm roots in the Linux world, but luckily they are also available for Windows and Mac OS X. No wonder I have them installed on my MacBook too.
The problem
On OS X, Inkscape and the Gimp are not completely native applications, but they depend on X11.app. This extra layer makes the user experience unfortunately less streamlined than with native applications. Especially the keyboard interaction of an out of the box setup can be clunky.