I admit I'm a terrible pair programmer, so my experience may not be representative, and while I sometimes get frustrated when the person with the keyboard fails to hit the right keys (and to be fair this person is sometimes me!), almost always the main source of frustration is when can't agree on something or when one repeatedly misunderstands the other.
On the other hand, when we are on the same page, slow typing is seldom a problem.
On the other hand, when we are on the same page, slow typing is seldom a problem.