As a Brazilian, I like that it exists and it actually works. I do worry about the concentration of power in the hands of the Central Bank, because, as an institution, it often vies for "independence" from the govt.
The biggest drawback, however, is that it makes criminals' lives very easy: they arrive, threaten you to unlock your phone, make a pix transfer and leave with your phone. The Central Bank and police always have a hard time tracing the money to the actual thieves, as the bank accounts used are "oranges", fake accounts opened in other people's names, often without their knowledge.
There's also a recent fraud that involved cancelling pix transfers: someone would "accidentally" send you money and, once you returned it, they'd cancel the original transfer, which made it impossible for you to cancel yours.