Also works well with the Energy Orb spell, making it easier to hit moving enemies with it and dig across long distances.
Reduces effectivness of the Homing effect, as the projectile will have less time to accelerate towards the enemy, so you should not speed up anything you want homing to effectively work with. On the other hand, if you have the Homing Perk you can use Speed Up to reduce (but not remove) the effect for specific spells you don't want to home.