Guinsoo's Rageblade is 75% statistically efficient with no stacks. Its stat efficiency increases by 8% per stack, becoming efficient by the fourth stack and reaching 138.7% stat efficiency at maximum stacks.
Alternatively, the item becomes 129.6% efficient while the user activates the passive at less than 50% health.
With all passives at their maximum value, the item becomes 193.5% efficient.
The unique passive ends after 10 seconds of neither dealing nor receiving damage.
Multiple Guinsoo's Rageblades will give multiple stacks for each autoattack and ability cast, but a champion can still only have eight stacks in total.
Guinsoo's Rageblade's unique combination of traits make it something of a niche item. It is best on autoattack-based champions who benefit from both attack damage and ability power (Jax), especially those who profit from being low on health (Aatrox, Tryndamere, and Poppy).