http://www.sheldonbrown.com/gloss_bo-z.html#brakelever

I do have road BB7s and they work wonderfully. I haven't got through the "break-in" period, either, but I get excellent response and power.

I'm not so mechanically inclined, but the difference between road and mtb BB7s are the amount of cable pull required to get the caliper to close on the rotor. Mtb brakes use a longer cable pull while road brakes use a shorter cable pull. This means that mtb disc brakes can be modulated a bit more while road disc brakes are less subtle.

I would recommend taking the bike back to the shop and have them make sure they installed the "road disc" version of the BB7s. Perhaps they put the mtb on by mistake. This would mean that you are using short pull levers (your Sora brifters) with a brake that requires a long cable pull.

Alternatively, perhaps they didn't set the brakes up correctly. Here's a video that helped me adjust my brakes:

http://youtu.be/NasGJFtgq0A