Full disclaimer: I haven't done much UI (outside of HTML/CSS/JS, that is)... I dabbled with Visual Basic and the associated tooling (WinForms, at the time) during my college courses.

Of everything you describe, I think the area I struggled most with was:

>getting your event routing / updating to happen in a __clean__ way.

I was a naive and young programmer, so I'll withhold any criticisms towards WinForms, but the event routing was a _mess_ by the end of that project.