Installed on a mediawiki 1.19.7 with PHPExcel 1.7.8. It doesn't show on the version page, but seems to be installed anyway. It successfully loads an xlsx spreadsheet, tables are visible. I can double click fields to edit things. Not sure if there's a way to save changes made, looks like only viewing for now. No formattting, it seems. Not sure if parts are missing because of the version of MediaWiki or because it isn't implemented in the extension yet, but very pleased I can view data at least. 13:51, 19 July 2013 (UTC)
Did some further testing, functions work, I'm able to add up ranges of numbers and perform other functions normally. From Spreadsheet-js, it looks like there are a fair number of functions working ( though I found 343 incidences of functions that just return "Not Implemented ). Here are the ones that have something, haven't tested them all:
"AND" "AVERAGE" "AVERAGEA" "CHIDIST" "COUNT" "COUNTIF" "ERF" "EXP" "FALSE" "GAUSS" "IF" "LN" "LOGINV" "LOGNORM.DIST" "LOGNORM.INV" "LOGNORMDIST" "NORM.DIST" "NORM.INV" "NORM.S.DIST" "NORMDIST" "NORMINV" "NORMSDIST" "NORMSINV" "PERCENTILE" "PERCENTILE.INC" "PI" "POWER" "RANDBETWEEN" "ROUND" "SQRT" "SQRTPI" "STDEV" "STDEV.S" "SUM" "TRUE" "ISBLANK" "ISERR" "ISERROR" "ISLOGICAL" "ISNUMBER" "ISREF" "ISTEXT"
ZombieWatercrest (talk) 19:23, 19 July 2013 (UTC)