Remember the colorful wisps from Sonic Colors (Or Colours in Canada and Europe?) If not, let me remind you. The wisps were items Sonic could grab to help his advance in the stage. These include the rocket, lazer, and drill wisps. They were the main gimmick of the game and they were pretty fun to use.
Lost World brought them back, along with some new ones. However, the wisp use in Colors is infinitely better than in this. The wisps are either unresponsive, a pain in the butt to aim or steer, just plain freaking sucks, or have a combination of any of the three problems I just mentioned.
One wisp, for example, is the new hawk wisp. While I find the concept of this one cool, it's very problematic. The thing takes freaking forever to actually start to steer this wisp. Even then, the first time you hit something while with the hawk wisp, it disappears, potentially having you fall down a bottomless pit.
However, most of these wisps are completely optional. I don't have to use the hawk wisp if I don't want to use it. Though, I still wish that they would make better use of these guys. They were great in Sonic Colors, and it's just a shame to see them downgraded to such degrees.