I have a project that contains speed buttons and pagecontrols with skin TB_BTN.
Sometimes the tabs are skinned properly, like in this MetroUI skin:
[attachment=8331:acTB_BTN_MetroUI.jpg]
Sometimes the tabs are not skinned at all, like in the next Opus skin:
[attachment=8332:acTB_BTN_Opus.jpg]
I would say, about 40% of the skins go wrong.
This is a project with which you can test it yourself:
[attachment=8333:acTB_BTN_skin.zip]
Many of the skins that go wrong are actually used by my project, so this one is important to me.