It's a solid pick-up. They needed to trade Moss, and then they needed a veteran receiver who could integrate into the offense quickly. Branch has been decent this year, and his injuries won't affect what he does within the Pats' offense. He reads the coverage and finds pockets to sit in. He's a chains mover. He's also a favorite of Brady's.
Jackson is not someone that would fit with the Patriots. They could still trade for Williams if they want to. Not like they don't have 7 picks in the first 4 rounds...