Well, in this case I use it for multi variable editing, but most of the time, it's for editing multiple cursors at the same time. As you get instant feedback, it is much much better than vim's macros.
You'reright though, it is mostly the same as vim's substitute (and you can use it as such: ":x/foo/c/bar" is the same as ":s/foo/bar/g"), but for complex substitution, it is sometimes better to type it directly by hand rather than trying a regex 3-4 times in a row, with undos between trials.
Since I learnt to use these cursors, I never looked back, really. The instant feedback really makes things easier.