One of the things I constantly tangled with in my campaign was the 'wuss factor' of the various enemies faced by the party. In the original iteration of the rules, a typical Stormtrooper was cannon-fodder, pure and simple—with a 2D Strength (+1D w/ Armor) and a 4D Blaster Skill (-1D w/ Armor). Though presenting a slight challenge to starting level characters (who averaged around 4 or 5D in their combat skills), these FodderTroopers were quickly outclassed as the characters gained experience. It got to the point where they were almost becoming a joke. That's about the time I started implementing the 'combined-fire' rule. This leveled the playing field quite a bit, but there still existed (and still does exist) a cockiness among my players (and their characters) that I find both endearing and (as a GM) challenging.
On the one hand, its good that the PCs 'feeling their oats'. They're powerful. They should be proud. But on the other hand, feeling too MUCH superiority takes a lot of bite out of the game. It's like the difference between a Jackie Chan movie and a Steven Segal movie. You know Jackie is good, but he still occasionally gets his ass handed to him. He has to work at it, and because of that, you root for him all the more—there is till dramatic tension. Segal, in contrast, never loses. In fact, in most of his movies, he never even comes CLOSE to losing. Then it becomes more a matter of 'how is he going to mess up his next adversary', not 'is he going to be able to beat this guy.'
Thus, for me, its a constant balancing act between letting the characters BE the mega guys (and gals) they are while still giving them foes they can 'respect'. There is a saying that I am too lazy to look up the exact wording of. It goes something like: "A person is measured by their enemies." If you have a bunch of weak enemies, then it belittles the characters in a campaign. But again, there is a flip-side: you don't want enemies that completely overpower the PCs. That TOO makes them seem 'small'.
Though the pendulum in my campaign has swung in both directions, I think I've managed to keep a pretty good balance—especially in the most recent enemy, the Nagai. They (and their various minions) are not unbeatable, but they ARE enough to give my PC's pause, making them consider tactics rather than barreling in head-first and trusting to stats. Likewise, all my players have a healthy respect for the lowly Stormtrooper—at least when he's with a squad of his buddies. I consider that a GM triumph.