Wexter said:

I don't think dialogue makes the stormtroopers more menacing. On the contrary - if they have the need to spell out even the most basic orders (blast them, stop that ship), then they really don't seem to be a really competent force.

It's a command structure....it's not because they're stupid...but because orders (especially in high stress situations) are always barked out....even when the orders are blatantly obvious.

Personally I think having them completely silent makes them less credible as a source of danger to the protagonists. Like I said in my last post...I wouldn't want spoken lines everytime we see a stormie on screen......but I think only 2-3 instances in the entire film where a stromtrooper says something would make them more credible. One to three word sentences only....like "yes sir" or "move"....that sort of thing.