James Lileks, American journalist and curator of 20th-century design and daily life, draws our attention to the sort of kitchen that you might have if you were buying new in 1939 -- and he comments in passing on glass-block walls. To wit: 'I never come across an old house that had a glass-block wall; wonder how popular they actually were'.
My answer is: not popular at all. Glass blocks seem like they ought to be a good idea, but the only time I really liked them was as a shower stall barrier in a 1970s add-on to a 16th-century cottage in England. It wasn't pretending to be a wall, much less a window, and it did let light bounce around a small space, while offering the stall occupant a measure of privacy.
But otherwise I don't like them. In a way it's surprising: I love glass, I love light and the play of light within or through glass, and I like privacy without wishing to drape everything in a burka. So why am I not fond?
An architect pretty much explains why.