I like 529 plan with conditions.
1) In Michgan, 529 can get you State Income write off (4.4% top $10000, you depoit today and use it tomorrow the annual return is 365x4.4%, remember is guaranted option only not equity option).
2) low cost
3) Not for young 18 year old which has a lot's of earning potential but cash poor(which will guarante a financial postion)
4) For folks who worry think govement money is too expensive to borrow.
5) Last the most important: 529 is designed for super rich who is estate trasfering not for education (nothing for them to spend for ebucation) for heavy estate tax break. And the lower your income and assset, the less you should think about 529. At what level of income and asset level to consider 529, I have no answer. Different school has different formula and that might change without notice.
So do the following: Contribute max to 401k, roth, pay down the mortgage and pay down the credit loan. Improve your debt/income ratio and credit rating, diversify diversify, teach your kids to take their responsibility for education, study hard and work hard treat loan seriously, pay down the debt and live in a happy life.