I've studied how Gravity is shaped rather extensively but I still trust it the most considering that I have been watching this product for several months (almost steady gravity), potentially meaning that a lot of people could have picked it up and made a successful sale out of it. I've also checked the competition on search engines and independent reviews, so I'm pretty sure this product converts especially by the time I bought and reviewed it myself, since I know the niche inside out.
I'm currently using PPC ads, so the keyword research will later come in handy I guess. Do you have any positive/negative clickbank experience ?