It is indeed considerably more verbose, especially the "context" version (the one focusing on semantics, rather than presentation), and I did not write much of it myself, but I can imagine it being fine. It should not be a bottleneck for carefully (and slowly) composed documents, while for more casual and quick notes, even with LaTeX it appears to be common to use both a preview (often inline) and some input assistance, avoiding completely manual handwriting. Besides, as the linked Wikipedia article mentions, it is rather like expressions in Lisp-family programming languages (or pretty much any common ones, if you avoid infix operators), which are not that bad. I imagine it may also be more convenient (and terse) in combination with SXML or KDL, to avoid closing tags.