PrEP is the first pill approved by the FDA that HIV-negative people can take prophylactically to help protect them from getting HIV. Patients must take the drug daily for it to be effective, which has led some to question whether or not the regimen would be adhered to. In some studies, adherence was a major problem. Regardless, earlier this summer the FDA rather controversially recommended that all people in certain demographics take PrEP.
Those opposed to the widespread use of this drug is that it's not going to prevent other STDs, which is true. However, they also claim that it may give people who take it a sense of invulnerability toward HIV and increase risky sexual behavior. However, a recent study at UCSF has shown there to be no link between the two. There's also the debate over using a drug for a disease you don't have. Truvada isn't exactly a sugar pill, so as with any drug, there is always the issue of its toxicity.
Still, making it more generally available to those who need and want to use it, and improving information about it for doctors and patients will hopefully be a good thing. Go here to see if PrEP is right for you.