I'm putting together some virtual machines to test different browsers and I'm wondering if there is any compelling reason to be able to test the same version of IE on different versions of Windows. (i.e. IE8 on XP and Vista) I'm mostly talking about testing CSS to make sure it "looks right" across browsers, but if there were major differences in JavaScript I would want to know that too.
Are different versions of IE "generally the same" on different versions of Windows? Thanks!