Sorry, I didn't try any polyfills; I had a few hours on a weekend and compatibility wasn't on my list. I did do that for a previous project[1] and it was more work than I had time for. I'd love it if Firefox included a CSSMatrix implementation, it's incredibly useful. That and a method to get the absolute transform of an element including all the fiddly transform-origin stuff would be wonderful (I remember roc talking about something like this, but don't remember what happened).
[1]: https://github.com/iamralpht/tboard a spelling game for my kids, inspired by the worksheets they get at school.