[wp-hackers] Can I use $query->set() (in a pre_get_posts() hook) with a custom taxonomy in WP 3?

[Rich Christiansen]

Hello, all!

I'm up against a wall here.  I'll demonstrate my problem with an 
example.  I can do something like the following with a standard category:

$query->set('category__not_in', $term_id);

But how do I do the same with a custom taxonomy term?

I'm thinking I could use '<custom taxonomy name>__not_in' instead.

This trac ticket seems to suggest that the functionality is available, 
but I can't make it work:
http://core.trac.wordpress.org/ticket/9951

I'm using Wordpress 3.3.1 if it is relevant.  Thoughts?

Thank you very much! :)
-Rich