Pardon if the docs say IE8 is not supported for these somewhere, but I didn't see anything.

The glyphicons do not work in IE8 or IE9, at all. The best example is just the example glyphicons page (http://getbootstrap.com/components/). IE10 and other browsers seem to be fine.