Calc with it's huge data-sets is the app that this would most likely benefit most from; I attach a small sample document and a callgrind profile showing the unzip + SAX parse + namespace resolution at >10% of document load time. 10% is not that much, but we other ongoing work to improve other calc core code performance :-)
Created attachment 77071 [details] sample sheet with 100k random doubles in a column
callgrind profile at: http://users.freedesktop.org/~michael/callgrind-load-doubles.txt.gz - download, gzip -d and run kachegrind to see the result (if you're interested).
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