What is this?
This is a prove of concept addon to show that it is possible to do actual round action buttons.
Additionally it is possible to use SetTexCoord values to change the border-radius.
Of course this addon is not complete. By adding round check/push/active state textures the addon could be finalized.
Just showing possibilities here.
SVN
http://code.google.com/p/rothui/source/browse/trunk/wow5.0/rRoundActionButton/