But that's what I see with generator like yeoman, bootstrap template and compass mixin, it's getting really fast to get a UI up and running. I mean making a quadratic color palette in sass is simple 3rd grade math, shading, grading and other color transformation are few mixin away. I can't have a function in photoshop that tell give me the best contrast on the font I use when I change the color of my button for example. And I am wondering how it has affected the workflow.

Exactly. You also get a much more unique look from PS.