I think many seasoned programmers forget that for the non-programmer, syntax is a sizeable impediment to getting a working program and so I'd imagine removing syntax as a source of errors would open up programming to more people.
Sure, you can come up with a more general purpose visual esolang (http://en.wikipedia.org/wiki/Esoteric_programming_language) but how would this match the efficiency of programming in, say, C?
I don't think this comparison makes sense — how can you compare the efficiency of a programming environment to that of a programming language?