This should be clear by now. If you want a box to be 10 mm wide, write 10 mm and you get it. Write Red setrgbcolor and you get a red. No hidden traps. No more moving parts of pictures around to get them centered.
Gilt is complete.
There is nothing more complete than postscript. We have all the features of all picture editors because they all use postscript at one step or another. Gilt is expandable. Gilt has a plugin interface which allows you to expand the functionality. For an example look at the cd table of content plugin.