We have identified a problem with Glyph Designer on the new Retina MacBook Pro which causes the glyphs to not appear on the texture or preview views. We are working on a fix for this but there is a temporary solution that will allow you to continue using Glyph Designer on these machines. Pulling up the info panel on the Glyph Designer app you will see an option to run the app in Low Resolution. Selecting this option will cause Glyph Designer to function as normal but it won't make use of the high resolution display. We hope to have a fix out for this as soon as possible. Thanks Mike
UPDATE
The issue was fixed in Glyph Designer 1.5.8 (1442)