I think you are much better off starting your own 529 plan, rather than using Upromise.
Upromise says that they estimate you might save 8K for college in 15 years.
http://www.upromise.com/content/howi...ngs.html?cx=l1
(click on "how you save" and then "view assumptions")
However, the assumptions are *very* unlikely - you probably won't save anywhere near 8K. Even if you do, this is likely nowhere enough for the college tuition costs your kids will face, so you'll need to save lots of other money anyway.
You'd also be better off shopping at cheaper merchants than the ones offered by Upromise or through portals that offer a better rebate (such as ebates). An example? Exxon is the gas station of choice. But Arco or an independent brand will beat Exxon's gas price by at least a dime a gallon, while Exxon rebates only one cent/gallon. You'll save more money for college by NOT using Upromise in these cases.
Other issues? Loss of privacy (upromise will know an awful lot about you), participating companies and rates may change, account can be terminated if no money is added in a one year span, the company could fold.
See also:
http://moneycentral.msn.com/articles...asics/7652.asp