I’ve heard so much for and so much against this (I’ll call it a pacifier here for your convenience), and still haven’t figured out where I stand. I was dead against them when my daughter was born, but it turned out to be a life-saver.
My problem as a parent (and I had a similar problem as a guitarist when it came to picks) is that they get lost, and then your baby can’t sleep unless you go out in the middle of the night and buy a new one. I solved the guitar problem by learning to play with fingers, and the pacifier problem by buying lots and lots of them, and hiding some in special places my daughter couldn’t reach for emergencies. Also, she loved them and their different shapes and colours, so I’d often buy her one as a present if she’d been good, she ended up having a collection of them that she’d carry around in a backpack by the age of 3. And she’d use different ones, she’d pick her favourite and suck on it, then put it back in the bag and pick another one.
It is true that they can harm your teeth, but you’ll change baby teeth anyway, so as long as you teach your kid to brush (somewhere around 3–4), it’ll be fine.
I also don’t like the idea of my daughter having a piece of plastic in her mouth, but the equivalent would be sucking on her own finger, which my cousin did until the age of 12. The good thing about dummies is that you can eventually get rid of them, whereas you’ll always have that thumb handy for the rest of your life (my cousin’s was almost sucked to the bone after those 12 years).
And after all, there are so many serious issues to consider when bringing up a child (eg keeping it away from the evil grandfather, making sure the aunts don’t kill it, dodging bullets and knives and making sure all this happens with a smile) that whether she has a pacifier in her mouth for a couple of years is the least of your worries.