I'm really sure that UI "improvements" like themes and any kind of non-standard controls is the absolute evil for the utility sets like Pirinform's one. You guys make the sysutils that support a bundle of OSes. The eyes of Win2003/2008/7 guys are bleeding. But my eyes (Win8.1) are bleeding too because actually that is not a Win8.1 UI but non-working imitation. Ask yourself a simple question - is there anything in the UI than cannot be nicely painted and aligned with standard controls. The answer is - definitely not.
If I was a project owner I would just terminate all the exercises with "themes" and so on "design" bulls**t and rollback the UI to something like CCleaner 3.x.