On IE8 (genuine IE8 not IE9+ in IE8 mode, windows 7), the four simple demos on your demo page don't run, and this error is in the console:

The 'Advanced usage' demos do seem to work, however.
I tried making my own demo on jsbin and it fails with identical errors: http://jsbin.com/ejiqov/1
[Strangely, after the first time I ran the script, it stopped failing with an error message - but started failing by ignoring the top: and left: values set by CSS. Edit- this second sub-issue can be solved by applying the positioning to an outer wrapper element and then applying the rotation to an inner element - but it would be nice if the transform calculation could take existing CSS top:, left: etc into account - working demo here http://jsbin.com/ejiqov/3 ]