I don't see how the chip would make any difference. Except maybe they won't need 600lb heat sinks and 55 fans in a Power Mac filled with holes. That would be awesome. Also - I wouldn't cut my hand everytime I had to reach inside the damned thing. If Intels do run cooler, we should get smaller form factors and more open machines (in terms of internal space.)
I'm sure they'll always be pretty to look at. Jobs is way too much of a design snob to make crappy boxes.