Of course its up to you to use it, but I see many problems with this unlock method. Even here from a recording the password is guessed after about 10 attempts if users are not well educated about choosing a secure Password. Example here. Given time you can try reasonable combinations by hand Traces on screen give hints about the correct position. It would be improved by a huge amount if you had to do 3 or 4 of such pictures. Best would be if one could combine different unlock methods. E.g. do a picture-unlock and then (without feedback if you where correct) enter a Pin (number positions randomized). This would combine the strengths of individual methods.
Your information is dated. I have double-tap-to-wake enabled on my XperiaX and I have never had any sleep problems with it.