I am using beta 3. I had a look in the db and saw that some of my event categories were saving to wp_em_categories, while others where saving to wp_terms. I'm not sure if this happened between beta 2 and 3. The categories that were saving to wp_em_categories seemed to be functional on the front end. To make a long story short I have made a mess of categories (categories deleted in admin continue to show in wp_em_categories and undeleted ones in the db don't show in admin).
I am starting over. I now seem to have categories appearing in both wp_em_categories and wp_terms (which I assume is the expected behavior?), but still cannot delete a category using admin from wp_em_categories (it does delete from wp_terms)