My baby girl started playing with this at around four months. At this point, it's mostly a chew toy (especially when her two bottom teeth came in), but she has loved it for a few months now. We've used it many times as a toy in the car and it keeps her happy. It's a classic for a reason and I've given it as a gift to my friends with babies. It's just the right size, too. Also the fact that it squeaks helps when she needs a distraction.
she's obsessed with Sophie. As long as you're careful about cleaning this then you should have no issues, just make sure that you clean it with a wet antibacterial cloth, any water that might get in the squeaky hole might cause it to get moldy on the inside!