Just discovered this and LOVE it.
It would be great if you could create rounded corner rectangles. Also the ability to see other characters as you editing / constructing a particular character would be lovely.
Good to hear!
Rounded corner rectangles are a good idea - I believe you can do this in Illustrator, then you could export / import SVG into Glyphr Studio. Kind of a work around, but once you have one, you can copy / paste within Glyphr Studio.
The current "Test Drive" page is not very useful. In Glyphr Studio v2 we're going to have the ability to see other glyphs around the one you are designing, and also have a larger page or separate window with sample text at multiple sizes. This is crucial for designing a good typeface!