My wife is a qualified professional ECE teacher. The vast majority of teachers and staff there are genuinely there with your child's best interests at the top of their minds.
The owners/management of the centers however are after your enrollment/money.
Visit the centers your are considering while they are open, if anything makes you uneasy with it don't go with that one. Especially if the facilities or the staff seem a little off. Trust your gut. See where the sleep room is, inspect the toilets etc.
If possible talk to the actual teachers and get their take on things: ask them what they do in their breaks, where they take them. If it sounds like that don't actually get non-contact breaks then your child isn't going to be getting the attention they are supposed to.
ECE is great for children, they play, make friends, and it really helps their social development. The hardest part is, as you say, leaving your child with "strangers" but they don't stay strangers!
Centers get audited by ERO the same as schools do. The reports are publication available from the ERO's website.