The description sounds very simple, so why do Boomerangs cost only 15 credits, and a Rock star costs 35 when they both last four hours? Simple, this one only affects (resets) PROFILE RATES, while the Stars affect (resets) LIKES. Liking someone, does not require you to go to their profile, and when profiles can be viewable to friends only, or require a salute, runing a Boomerang while restricting your viewabiliy, can significantly effect how well it works for you. One ideas is to change the viewing to everybody for the duration of the power up, then change it back. Do that if you want to make more work for yourself.
Also, people often think that running any power up will attract people to like you, so why not just run the cheapest power up. Simply put, you get what you pay for. The investment in stars far outweighs running cheaper boomerangs.
The boomerang by itself does just what it says. There are two specific undocumented things.
1. For level 39, users must be rated 11 by any top 250 lifetime, which is automatic if they rate any top 250 who is running a boomerang. Even if they rate 10, the return is always 11. Do ten, and that part is done. You should still friend request as many top 250 as you can, because reaching level 40 is when you start really playing.
2. Two other power ups, FAMPlifers, and Big Bangs also reset the ability to rate your profile. There are ways to run any two or all three of them and one or more extra rate reset. Since this blog is dedicated to each power up by itself, I will write one blog specifically for that.