In December 2012, the introduction of plain packaging gave the Australian government full control over the design and appearance of cigarette packs. Tobacco branding was abolished and tobacco companies were effectively prohibited from using their intellectual property.
A few days before the policy went into full effect, activist-researchers announced that plain packaging had the effect of making some smokers believe that their cigarettes tasted worse (a hypothesis that was eagerly pursued by those who hope the policy will be extended to 'junk food'), but empirical research about the revealed preferences of the Australian public has taken longer to appear.
Two years on, we now have enough data on tobacco sales and smoking prevalence to say with confidence that plain packaging has had no positive impact.
Go look at the facts and make up your own mind.