Brachiation: Limited use movement through trees. Does not really address the issue of how one moves through trees and use feats like Spring Attack or Shot on the Run at the same time. Not broken, though if you adventure is set in forests all the time, could be annoying.
Danger Sense: Rerolling Init once per day isn't broken, though I think the "reroll X once per day" feats are a little on the weak side.
Hear the Unseen: Allows you to determine the square of invisible foes with a semi-difficult listen check (one a lvl 10 scout would make half the time). Doesn't remove the miss chance, just remove the guesswork. Though it is not explicit in the description, I would assume this works for one round only---once they move, you need to recheck. A useful feat in certain situations, but I do not think it is overpowered.
Improved Swimming: In a Savage Tide like campaign, this feat *might* be worth taking. In other cases, like Brachiation, is too limited to be broken.
Quick Reconnoiter: This feat gives you a +2 Init as well, which stacks w/ Improved Initiative (+6 total). This feat is useful against opponents which are hiding (snipe and hide tactics) in combat. It also can combine with Hear the Unseen to make that check a free action instead of a move action. Not broken, but powerful.
Any other discussion before a vote?