The Speed powers are awesome. They give offensive ability in the form of initiative, defensive ability in the form of dodge bonuses, tactical movement bonuses in the form of reflexive movement AND sprint roll bonuses, and they give stealth bonuses (which are useful in and out of conflicts). You get bonuses to Athletics, Alertness, and Stealth.
In comparison, Strength powers are purely offensive. You get a bonus to Might, and to whatever rolls are modified by Might.
Toughness compares even less favourably.
In short, Speed powers rock the house. They're not quite broken like Dexterity and Celerity in the old World of Darkness, but they're really good.