The Themebuilder is way too narrow for me to style the product we are building properly. As a designer, I would like to be able to style most properties using a tool like that. E.g. I cannot style the grid except 3-4 properties. The example grid has no hierarchy, and most grid functions are not there for me to see/style. I have worked with your competition Infragistics before, and they have a very flexible AppStylist that allows me to change all style properties. 

I would like you to build something like that! And, of course, be able to import current CSS and not start from scratch every time...