Re: "After Earth" - what would the world look like?
Don't forget that we had fur until we became bipeds. The fact that we don't is an adaptation to heat loss for long-distance running, which bipedalism made possible for us, but most biped species do end up as runners, don't they? And you need grasping hands first, before the bipedalism, or the front limbs will just atrophy (T. rex rats!)
Generalist, rodent-like creatures are a good evolutionary starting point. The ancestor of all living mammals was similar, as was the first marsupial that colonized Australia and diversified into the marsupial wildlife we see there today. But that's without other mammals already filling all of those niches. For a mass extinction event, you'd expect the little rodent-like things to be the most likely to survive and also be the most suited to diversify into unoccupied niches, but just removing humans, who aren't in any particular competition with rodents now, wouldn't really change their opportunities all that much.
It's hard to imagine where sapience might evolve again, because it happened more or less by accident the first time - primarily a result of pressure for the parts of the brain involved in handling large social groups and the parts involved in toolmaking, I think. But I think the article's right that the first thing you'd see with the removal of humans would be the return of the large herbivores and their predators - we wiped those species out recently enough that even if we weren't exerting any pressure on those niches today, they still wouldn't have bounced back.
Really, next up for developing sapience might be the dolphins, if they're not there yet. = )
I know I shouldn't use tildes for decoration, but they always make me feel at home~