There was an article in Flight International a few months ago about a survey done on airline pilots when they fly manually in IMC. They managed to do everything perfectly. But when a survey was done on their scan method (looking at their eyes I think), there was no proper scan pattern at all! But they managed to 'pass' because the end result was good - maintained heading & altitude etc as necessary.
The conclusion? Sheer luck they passed. They have completely forgotten the instrument scan pattern. An accident waiting to happen?
The same can be said about visual flying too I guess...