Fireballs, as said above, are less awesome than they in my opinion deserve. I think, while REALLY cool, the arc they take is too pronounced, and hence, un predictable, this makes using them.... not... well just not as good as taking the short time to charge a hue blast attack instead.
Perhaps if somehow, they were a very fast, ranged attack option, it might offset this?
the megablast attack is EXCELLENT and feels great, so I would personally disagree with changing that to make the fireballs more useful.
As I said, I feel a really fast projectile, in a very predictable direction would make these much more useful. Perhaps the cool arcs could be represented only graphically, to keep that cool factor the fireballs currently have?