The Scorpion tank made difficult sections of the first game seem like shooting fish in a barrel, with only Wraith tanks and Banshee flyers posing any serious danger. In multiplayer, using it was more of a tradeoff, as the tank could be slowed by the effects of plasma weapons, and the driver was vulnerable to being sniped, as are Warthog drivers.
In Halo 2, that trend continues; although the Scorpion cannot be simply boarded like the other vehicles, it is possible to jump on the tank and melee the driver.