Why change something good?
Well if you look back in history that charge could be laid at thousands of products or cultures if it comes to that. There have been loads of design icons which people at the time said could not be bettered and yet things move on.
When I go into an Apple store year last year, this year, next year one expects to see new things and yet!
When I go into my local Apple store visually (I'm not talking internals here) the present iMac looks pretty much the same from the front as it has done for quite a few years now. The Apple Cinema screen looks pretty much the same, the Mac Mini looks pretty much the same as it did four or five years ago.
The Mac Pro is certainly different - well done Apple, the iPhone has evolved though I simply hate the new form factor and as for Laptops - I never look at those whoever makes them as it's not a form factor that interests me.
I'm also not much interested in iToys, though I do have an ATV plus an iPad.
All in all then for me at least I don't go in much any more as it's a pretty boring experience.
I'm sure if BMW or Audi was doing the same with its vehicle line up then sales figures would be pretty bleak and the designers would be looking for new employment.
Of course I understand people with iMacs rushing to Apple's defence, they've spent a shed load of money and need to justify their outlay.
I too like my iMac but I just thing it's way past time to try a new approach to the form factor.