I'd say give it a few days. I'm guessing while you did the brakes, you manually turned the steering knuckles to more easily reach the bolts and such. In the process, you may have introduced air in to the system, hence the roughness in the power assist. After a few days of driving you'll likely work the air out the system. It's not all that uncommon for this to happen, and it seems to get worse the faster you manually turn the steering knuckles.

-Rod