It will be fine, just make sure you tension the headset well: Sheldon Brown says you can tension it just with your body weight, but I find a string tied to the stem and the fork works much better.
http://www.sheldonbrown.com/handsup.html

To the naysayers: smarter more experienced people than you have recommended worse.


OR, do like Burton said and just use the locknut to tension the threadless headset.