I've added an optional radius for rectangle corners, for use with the DrawRect() command, along with a new gradient mode that uses a second color to draw a linear gradient on primitives. I like the interface for the program Vue, and I am modeling my default widget scripts after this style.

Here it is rendered at 800% scale. This is rendered directly on a window and sub-pixel antialias is used (Microsoft ClearType):

The appearance of the button widget at this point is something I would be happy releasing in a final product. Of course you can modify or replace this script to meet your own needs.