[glopes]

I've been developing a visual reactive programming language, Bonsai (https://bonsai-rx.org/) for the past 8 years and it's proven successful in neuroscience research. It is an algebra for reactive streams and addresses some of the issues raised in this thread about GPVPLs:

a) it's amenable to version-control;

b) you can type/edit a program with the keyboard without the need for drag-drop;

c) the auto-layout approach avoids readability issues with too much "artistic freedom" for freestyle diagramming languages like LabView;

d) because its mostly a pure algebraic language w/ type inference there is little complicated syntax to juggle;

e) the IDE is actually faster even though Bonsai is compiled because there is no text parsing involved, so you are editing the abstract syntax tree directly

It definitely has its fair share of scalability problems, but most of them seem to be issues with the IDE, rather than the approach to the language itself. I've never probed the programming community about it, so would be curious to hear any feedback about how bad it is.