It's the big question at the end of the shot, and surprisingly, there are some really good and bad ways to answer it.
Before responding, I always try to get the okay from my focus puller, to be sure that he or she is satisfied. If there's a focus problem, there's no point yelling “Great!” and then having to retract that statement.
One answer to “How was it?” is “Great!” or wonderful, excellent, terrific, etc., delivered at a good volume with plenty of enthusiasm. It's your assessment of all the variables and clearly states that you feel production can move on.
The only other answer is, “Let's do it again. It would be really great if….” ...