Is there a way to check if the editor is using the Pro skin?

There are some tool icons I'd like to switch based on the Pro skin settings.

Checking shows SceneGUISkin with the Pro skin enabled and InspectorGUISkin without.

Is that a reliable method? Or is there a flag somewhere?

For versions before 3.5 this seems to be a better hack:
isProSkin = (EditorPrefs.GetInt(“UserSkin”) == 1);

In 3.5 there’s a new EditorGUIUtility.isProSkin property!