The Spectre is basically a Covenant Warthog that can boost, strafe, carry an exta passenger, and even rear (which can be helpful to thwart incoming collisions, or simply to climb over obstacles). In return it’s fire power is both weaker and more inaccurate than that of the Warthog.
I am bringing this up because I’d like to see it’s return in Halo 4. Rather than just one armed transport vehicle, we could have two. One aggressive (the Warthog) which focuses on attack power, and a more passive one (the Spectre) which focuses on movement and transport. Both vehicles are capable of doing both tasks, but they only excel on one task each.