Well, we've seen the Imperial guards now in ROTJ and AOTC. While they present a striking visual image, they've never done anything, they just tend to stand in the background. I'm hoping that we'll see them in action in Ep III. We don't know their purpose, their powers, their weapons, or their training. I'm not interested in EU stuff, because Lucas' movie vision of these bodyguards is the only one that counts. So...why would Palpatine need a special detachment to protect him? Why would he discard the old Blue Guard that had probably been used for hundreds or thousands of years to protect chancellors past? I can only speculate that he has created these commando type soldiers to protect him from the only enemy capable of hurting him - the Jedi. Darth Sidious is fully capable of protecting himself from mere mortals. But if the Jedi were to mount a sustained attack on Darth Sidious, he would need help to fend them off. I wonder, then, if he secretly trained these soldiers, teaching them ways to fight and even defeat the Jedi? And when the Empire finally comes to absolute power in Ep III, will they finally be unleashed in combat against their sworn enemy?