The halfling doesn't appear to be the weakest race of the lot.
Humans can pick an additional at-will in their class. To me, that's pretty useless. It means you already picked the two you most wanted, now you get to pick #3. Plus, you only get a single +2 ability bonus. Sure, you can put it where you want, but when you pick another race, most people pick it according to the class they'll play anyway so they get +2 in their major ability and another +2 to boot. The additional feat and trained skill are interesting, but then again you already get plenty of feats (over time) and trained skills anyway, so there's not much there. I don't feel the human gets anything interesting, the feat probably being the best out of the lot.
It sure seemed to me like Humans were intended to be THE Paragon multiclassing race. An extra feat allows them to slightly reduce the impact of their multiclassing, and nobody minds dropping a bad at will for Twin Strike or Righteous Brand...