It is nice that you can compare vehicles by mileage ratings, but you can't list, say, pickup trucks in order from best to worst mileage. The site also explains auto terms like PZEV, Hemi and ULEV, so that's good. It's also cool that there is a "Hybrid Center" featured prominently on the KBB homepage, but unfortunately. it's quite lacking. KBB explains how hybrid tax breaks work, for example, but this page is horribly out of date ("Tax credits will go into effect on January 1, 2006"? And the "ACEEE estimates that the Toyota Prius will get the highest credit"? The tax credit for the Prius just got slashed at the beginning of the month). A page for diesel advancements does not mention Ultra Low Sulfur Diesel at all, and it really needs to. Update, people, update.
[Source: Kelley Blue Book]