The problem you are likely to face is in the reach of the brake calipers. When you go from 27s to 700c you add a little more distance between the brake mount and the rim. The plus side is you get great clearance for fenders! The down side is regular short reach brakes might not make it to the rim (pads rubbing tires is very bad).

Look for long reach calipers. Harris Cyclery has some decent Tektros for $50.
http://sheldonbrown.com/harris/brakes.html#brakesets