Do you think that ideally it would be preferable to add columns to the term_taxonomy table, rather than using the options table for the custom fields?

It would seem to make sense to me logically (your custom fields are stored in the same place as the description, slug, etc.), but maybe there is a downside I haven't thought of…

Thought it was just for original categories at first.
But how do I get these values from the theme?

I want to know if I can append this to custom taxonomies in WordPress 3?

I was doing a demo for a friend and it became quickly apparent to me that he was not understanding the concept of having to add taxonomy metadata on a separate screen if he was adding a new term.

That got me thinking about the entire UX with the new tools that wp is giving us. It seemed like a natural progression to allow editing within one primary screen of all needed input information. Obviously not necessary, but it does help make wp more user-friendly.

I was thinking of using a lightbox or modal window pop up for adding in the new data. Anyhow, mostly just a concept right now.

If so, this isn’t something I’ve looked at yet. It would probably be a GUI nightmare to attempt this but I’ll look to see if the hooks are in place to make it possible.

By any chance have you had to extend this for client sites in the post_type UI?

What I mean is I'm guessing you are using this with a post_type, where when adding a new 'product' the admin would select an existing 'manufacturer' taxonomy from the select box, kind of exactly how we add categories to posts.

I've been working on the scenario of what happens when adding a new post-type 'product' if the 'manufacturer' taxonomy term does not exist yet. Currently we only have the ability to add the term, but not the custom fields belonging to the term from the post-type UI.

This forces the user to leave the post-type UI, and then go to the term UI to add in the extra fields.

To date I have not seen anyone attempting to do this yet. It just seems like a logical step to make life easier on the user inputting the new 'product', to be able to add a term + term custom fields, within the add post UI.

Either way, thank you, this is a great start for me.