They might look right, but they don't behave right with screen readers and other assistive technology tools, or with software designed to programmatically access, automate or test GUI controls. So it's a shame more software projects don't use wx, which for the most part doesn't have those problems.

QGIS, for example (that's Qt4 app).

While it is a great apps, UI-wise it is exactly as masklinn wrote. It has weirdness-es on all - Windows, OSX and Linux.