Solved! To make Bunny’s Technorati Tags fully compatible with WordPress 2.0 you need to change two lines in the add_tags_textinput() function.

Just replace this:

function add_tags_textinput() {
	global $postdata;
	$tags = get_post_meta($postdata->ID, 'tags', true);

with this:

function add_tags_textinput() {
	global $post_ID;
	$tags = get_post_meta($post_ID, 'tags', true);

The problem is that it will show existing tags, or let you add a new tag, but it will lose tags when you edit a post. It’s not able to retrieve the tags to fill in the form field, apparently because $postdata isn’t returning the ID it expects.

I’ve submitted the fix to, so if the author is keeping track of tickets there, the fix should show up in the next version of the plugin.

Update Jan. 3: The plugin author has released version 0.5 with a slightly different fix (plus a few other improvements), and it’s now compatible with WordPress 2.0.