This is a minor issue, but wanted to make you aware…incase it has not been mentioned.
When opening a glyphs document with multiple masters, the Font Overview tab always defaults to the first master, in most cases, the lightest weight. The issue is with the toolbar icons indicating the active master. The rightmost icon ( heaviest weight ) shows the active state, instead of the first. It seems to occur with any number of masters.
Glyphs 2 Beta (679)
Mavericks 10.9.5
I cant reproduce it. Can you make a screen recording?
Linked below are two screencasts…
Master-Icons.mov
references the issue in the original post
Window-Resize.mov
shows a small interface glitch when resizing the application window
Lastly, it would be nice if glyphs could remember the Sidebar Pallete visibility preference when launching.
The pallete is always visible, even if it was closed when quitting the application. Just a thought 
Screencasts: http://ge.tt/4KEY0T82
Thanks Georg!