The engineering sophistication is significant, but not in your face. Instead of cramming more electronics into the box, they work hard to reduce the parts count and increase battery life, among other things.

The engineering that went into the A4 is quite significant, but you wouldn't know it was there - except that the UI is very responsive, the unit runs cool, etc.

So you are right in a sense: people don't buy Apple products for the engineering - it's the design. But the engineering makes them not crappy. So they keep Apple products because of the engineering.