I think it's pretty safe to say that dataflow is one of the most severely underused programming paradigms today.
(I'm not fond of "visual" programming however, except where it opens new possibilities to someone who would never dream of programming the "real" way).
Ptolemy is an academic project work looking at. From this perspective, its an attempt to incorporate some of the advantages of 'real' programming into a visual environment. http://ptolemy.eecs.berkeley.edu/ptolemyII/ptIIlatest/
(I'm not fond of "visual" programming however, except where it opens new possibilities to someone who would never dream of programming the "real" way).