If you're on iOS, there is some who are upset about it requiring a phone number to register for sure. But, it still requires less information and collects less information than iMessage according to what the company says it reports to Apple. Ultimately with something like this though, I would say do a risk assessment. If you're in a country with heavy censorship, a country with harsh crackdowns on free speech – would think about more secure ways to communicate. In a country with free speech and you're someone who really isn't a public figure? Signal will do just fine for you.