The user experience of WinUI 3 isn't the worst I've seen but the developer experience is absolutely awful. I tried to make a simple app with it and the number of hacks I needed to get it to look and feel the way I almost wanted was horrible. And the documentation sucks. I had to read the system level implementations of controls in order to figure most of it out. It's great those implementations are available to read, at least, but OH MY GOD

Also seeing stuff like text fields re-implemented from scratch in XML scares me. I don't like to see that.