As a 5hr student, I don't really have the experience or knowledge to judge anyone, but I must say that I would be pretty unsettled by an instructor who fretted and grabbed at the controls all the time.
The two instructors that I've had have so far been cool and calm, and tell me how to put things right, rather than take immediate control. The only time he's done so was when my taxying went awry - I'm clearly more of a danger on the ground than in the air!
