I've recently become a massive fan of John Gruber, author of the Apple-focused technology blog Daring Fireball, through the 5by5 podcasting network (he's on The Talk Show). He has a wonderfully thorough, insightful and level-headed take on, well, most everything. This presentation he gave at the Webstock 2011 conference in New Zealand offers a fascinating overview how Apple has consistently innovated with their graphical user interfaces (GUIs) over the past 27 or so years.

The devil is in the details.