One of the things is a KDE style, I call Note, although it could be called flat.
Also, I'm trying to look at Qt designer, with some trouble, because there is something in one of the source files that totally drives gcc insane, making it eat a bazillion megabytes of RAM.
The generated XML files are very readable. I am curious whether there is support for runtime loading of them. I used to use that with Kdevelop's dialog editor instead of the code generation route, and it's much cooler.