Still needs refining:
1) Every search in private mode (done through the omnibox or the searchbox next to it) redirects you to a page which allows you to choose a search engine again.
2) Every search in private or normal mode shows a coin toss. If this animation is not relevant to your business model (brand positioning, monetization, etc.) then remove it. Having the search query pass through presearch.com and then redirect makes it slower, but having this animation shown every time, makes it annoying. If you insist on keeping it, try to make the animation shorter or change it to something else. It really. is. Annoying.