Are all side-pull road bicycle brakes compatible?
One thing to look out for is the size of the drop from the bolt securing the brake to the frame, and the brake blocks, to ensure the new brakes will fit in such a way that the blocks line up with the rims.

Probably if you have a newish bike, then any new brakes you buy will be of the same dimension as new brakes. But it's worth making sure they'll fit - more here:

http://sheldonbrown.com/calipers.html#reach

I recently bought an old steel frame and had to get some long-reach calipers as my spares were all short-reach and the blocks would have clamped on the tyre, not the rims.