Charles D. Clifford posted at HBO about an article on xbox.ign.com giving their impressions of Warthog driving in Halo. Simply put, they were impressed, and they'll be talking in more depth about why later:

The whole jeep/passenger system is actually just an example of Halo's overall brilliance that we'll get to in a later round of impressions. But it's the vibrancy, attention to detail and inherent logic in the world of Halo that makes this game so engrossing.

They also called the control scheme for vehicles in Halo one of the most clever innovations in videogames. Encouraging indeed!