I've wondered on this question also, so thank you for posting. I'm a little surprised at the number of people who feel the 529 isn't worth it. Why wouldn't it be?
Even if you live in a state with no state income tax, if you fund a 529 when your child is young, the dollars saved from not paying taxes on those earning should put you ahead, correct? Granted, that is assuming you don't over-contribute and your child does in fact go to college.
I personally opened a 529 with $15k for each of our children when they were born (actually opened prior to their birth in my name, then transferred to them). If market continues to perform, that should equate to 75-100k when they are 18, which adds up to tax savings on 50-85k in income. Worse case, if one doesn't go to college or doesn't need financial assistance, I could transfer to the other child, or myself, or grandkids, etc. I also like that it ear marks the money for the kids' education, so I can just forget about it and move on.