I'm implementing a brand-new GUI application in Win32 right now, for three reasons:

1) It's going to be used in conjunction with other legacy applications that only run on Windows PCs anyway.

2) GUIs designed for both phones and PCs don't work well on either, it seems to me.

3) In fancy high-level frameworks you often eventually end up calling a bunch of Win32 functions, so I might as well learn it. :)