Interesting sidenote: I was wondering how well-known the <gallery> attributes are. Searching for "gallery perrow" in the gallery namespace [1] returns 12 results (it says "showing 1-20 of 46", but never mind :-)
So, not the most popular thing, apparently. I'll still fix the script to honor the settings tonight, if noone beats me to it...
Magnus
[1] http://commons.wikimedia.org/wiki/Special:Search?ns0=1&search=gallery+pe...