For prototyping UI it's actually amazing.

"Add a sidebar to the side that tracks where we are in the document".

"Move all elements in area A into a split screen view with those elements at the left hand side and the remaining elements in the right hand side"

The above sort of thing can be painful to do manually. Changing a layout which can have 100's of elements and moving everything across to the new layout structure. Often you can waste a day tweaking it in various ways. LLMs are actually pretty amazing at it since it's a job where you "put old things from one context into a new context" and that's basically what they do. As in AI has saved me some of the biggest pain points and allowed me to focus on the meatier aspects of the code (which it's not so good at).