1.They DO have dells as servers in the main pixar office in USA, i work in Mèxico (they are now editing some parts of the films that are customized to the language in the region, this case spanish). But they DO have xserve as well, see, windows is basic on all officed work, as of the apps used on all the design team, 100% apple computers, are private branded, made BY Pixar FOR Pixar. And it does matter the Steve Jobs issue, in a technical point Disney bought pixar, but it was bought with stocks, that made steve the chairman, and Disney, as far as it looks like, will go on all animated movies when it comes to cartoons, we have 2 projects on the go for next year, both animated,the difference only looks this way:
Disney presents a Pixar picture
And by the way, Pixar originally was software for NeXT computers, lots of imaging software was Pixar.