I actually think Sam gets quite a lot of stick from some of our fans, most which are unwarranted.
Personally, looking at the other goalkeepers in this league, I don't think theres many/if any I would replace Johnstone with. (when you factor in age etc).
Some fans slate him for his passing out, that's how hes been told to play, some of the goals hes been blamed for tend to come from mistakes in front of him. Johansen for example got caught in position, followed by a pass which completely split our defence which struggled to close down Freeman, resulting in him scoring from close range.
I'm happy hes our number 1 at the moment.