When I'm editing a normal tex project the processor usage is about 30% (just typing in the tex document). When I'm viewing a generated pdf document, this goes up to 50%.
In contrast, typing in TextEdit is approx 5%. Viewing a pdf in Preview is about 10-20%.
This is on a single proc G5 1.8GHz btw.
Anyway, the question is, could you optimize iTexMac2 in such a fashion that it is not such a processor-intensive application?