Actually, you can have the buttons in Mozilla (1.3+) and Firebird (0.6+): just save a copy of your current edit_entry.tmpl and bm_entry.tmpl (in MTPath/tmpl/cms/), then replace them with the modified copies from
Blogzilla (for edit_entry.tmpl) and
Adam Kalsey (for bm_entry.tmpl), and you should get working Moz buttons while still having working IE buttons.