A solid breaker against medium-power sentries. On the positive side, it is a whopping 5 power for 3, which is more efficient for 4 or higher strength sentries than Femme Fatale or Mimic. It also works on its own, unlike Dagger or Switchblade. So, with Ninja you are more safe from sentries like Ichi 1.0, Taurus, or Uroboros. However, against stronger ice like Archer, get ready to spend 6 on power.
Overall, like all Criminal breakers, it is very powerful but inflexible. You spend a lot of credits for lots of power, in many cases more than you need. It will be more efficient than a Femme Fatale in pure power but lacking in her useful ability. However, there are few stable sentry breakers, so this can fit into many more decks than Aurora or maybe even Peacock.