I have it and rarely use it.
I greatly dislike all the extra markup that gets added to the XAML files, and prefer to know what I’m doing to just dragging/dropping items.
The few times I have used it have been to pull out the default styles or templates of a control, or to build something like a gradient, animation, or path, and then copy/paste the XAML into my project.
It’s nice if you’re into drag/drop coding, or if you’re working on a large enough team to be have a separate UI and Coding team, but other than that I don’t use it for solo development since I have to maintain the XAML mess it generates.