I think the approach taken by Notch is more like playing around with an idea to see if it works. The fact that he now runs a multi million dollar business doesnt seem to have changed this and its probably a good thing. We all have unfinished/failed projects laying around somewhere..he has is just way more popular than most of us and has chosen to make his development efforts somewhat public, which might have been a mistake as he now realizes.

IMO, hes still building games with the right attitude. He plays around and tries to find a cool idea, just as he has done before.