A group of boomerang throwers with the 3-1-0 upgrades (Glave Ricochet and Faster Throwing) can be used for crowd control and easly dominate most non-M.O.A.B. class bloons with the help of a 0-2-0 monkey village.
A boomerang thrower with the 0-1-4 upgrades (Faster Throwing and M.O.A.B. Press) can be used to delay a M.O.A.B. B.F.B. or Z.O.M.G. bloon for a short time.
Prior to the Version 7.0 buff, the description was "Throws 20% faster" but was changed because it was inaccurate and misleading, and also because this upgrade received a small buff to the attack speed bonus.
The patch notes for Version 7.0 are misleading; "20% --> 25%" was again actually referring to attack cooldown percentage decrease, which truly speaking is actually an attack speed increase from 25% to 33.33%.