Cela laisse à désirer = There is room for improvement; It is not quite the thing.

Je ne laisse pas d'être inquiet = In spite of all that, I am anxious.

[Here we have the old meaning of laisser (= laxare) to leave off. Hence, I do not leave off being anxious.]

C'est à prendre ou à laisser = You must take it or leave it; It's a case of Hobson's choice.

Il se laissa faire = He offered no resistance.