The folks at Bohemian Coding have released Sketch 2.1, with an emphasis on Retina display support. The update required many coding changes and "more than a hundred" graphic updates.
Sketch is the Apple Design Award-winning vector graphic app that's great for web and UI design, icon design and illustration. You can watch a demo video here. In addition to Retina display support, version 2.1 offers support for multiple borders, shadows, inner shadows and glows.
Sketch requires 64-bit Mac with 10.6 Snow Leopard, and can be purchased from the Mac App Store
