Does the latest IE9 Developer preview (Build 4, v1.9.7.9.16.6000) support the file API? The file API I am referring to is: http://www.w3.org/TR/file-upload/
Caniuse.com says the support is uknown and Wikipedia says it is not supported but doesn't specify what version of Trident it is referring to.
Unfortunately I don't have a windows machine with Vista or 7 on to test at the moment..
Using the File API test from Mark Pilgrim's page I got a false, sanity checked in Firefox 4.0 nightly and Google Chrome 6.0.490.1 dev and both returned true.
Note that Modernizr.js doesn't appear to work in IE9 build 4, so it could be the detection script is inaccurate.