Tabs are a nightmare to deal with when you want to align the columns. Also, I don't consider tabs to be human readable: They are too easily confused with spaces. (Case in point: make)
I'm not attacking your overall idea, btw. I've just given this a bunch of thought myself, and the design space is very tricky. My current approach would be to use ASV (ascii codes 27-31) and abandon 'cat'-based readability in favor of a 'vcat' which gives you a better visual representation. Of course that has its issues too.. :)
I think the point is that it's largely a formalization of what unixy tools already do.