We had one for our daughter. We didn't start it until she was a teenager, then she lit a fire under her tail and started college at 16 years old, graduated with her Bachelors at 19. So we didn't have much time to contribute to it. But what little we did do paid for a year and was a big help. We had to take out loans, stay away from Sallie Mae loans!
She went on to get 2 Masters degrees by the age of 23, now working on PHD. Her husband finished up his degree, is a teacher, graduating in May to become a principal. They are in debt. It sucks, but it is what it is.
If you can start a 529 plan now, get after it. Every dollar counts!