A niece did, but ended up with a full scholorship ride for college and used the 529 earmarked savings for something else. No penalty but it was taxable income.
I have always been turned off by the fact it's strictly for college... I am not set on my kids going to college and getting a bunch of debt then still paying on it 20 years later and not using the degree....oh yah that's my situation....
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!
Instead of a 529 plan, have you considered Roth IRAs? Contributions to Roth IRAs are with after tax money, and you can withdraw your contributions (not earnings) at any time without taxes or penalties. (You will have to pay penalties on any earnings from those contributions if you withdraw them before age 59 1/2.) Both you and your husband can have a Roth IRA and each can contribute > $6,000 a year. If your child also has earned income, he can contribute to his own Roth IRA, and while I don't know if it still the case with the new tax law, low income earners could earn tax credits for contributing. One of my sisters-in-law made contributions to an IRA and was able to earn tax credits for those contributions. And the good thing about Roth IRAs is that you are not locked into using it only for college. You can use it for any purpose. Thus, if your child does not go to college, you can leave the money in the Roth IRAs and let it grow for you and your husband.
Please consult with a financial advisor before doing what I suggested, but the way I see it, Roth IRAs are the way to, rather than 529 plans.