Eric,
Have you estimated your possible annual contributions from Upromise? That should be a critical criterion based on the comparison you are describing.
That said, I am not the sort that uses fees as the sole (or even primary) deciding factor in selecting any investment vehicle for any purpose. So I won't to make a recommendation to you on your specific question.
If you find Upromise to be an attractive option, have you considered opening two 529s? - one that you link to Upromise (making the minimum monthly payment to avoid annual fees) and the other being your primary 529 selected for other criteria?
TJ
[This message has been edited by tjb_nc (edited September 10, 2001).]