With dual-core processors flooding the mainstream PC market and today's launch of first quad-core processor, it will be very useful to have processor intensive tasks in IDE multi-threaded. The first tasks to multi-thread would be compilation and inspections.
I am not expert with these, but as dependency analyzer is already build passing compilation tasks to blocking queue and workers should not be very hard. Also inspections should be relatively easy to multi-thread. In order not to sacrifice single-threaded performance, workers could be called directly and sequentially if machine has only one processor.