This idea has been discussed on the usability mailing lists before.  Is it possible to implement these circular dialogues as replacements for traditiohnal toolbars?

http://www.daimi.au.dk/~kamstrup/articles/G3-ideas.html

There are a number of advantages from these.  Modeless Floating palettes are extremely functional, such as the much lauded ones used in the Lotus office applications.

A circular area would reduce mouse movement and create a larger target zone for the mouse.

Finally, not to be underestimated, these mock-ups look distinct and stylish.  They would help to differentiate GNOME from other desktop experiences.  If they proved to be usable and also helped to assert the GNOME "image" in the minds of users, they would aid us in forging a unique identity for our desktop.

Other information:
This has been discussed on the usability forum mailing list here:

http://www.mail-archive.com/usability%40gnome.org/msg02364.html