Category slug field missing with registered custom taxonomy

The value for global_terms_enabled for multisite is stored in wp_sitemeta

http://wordpress.org/support/topic/plugin-edit-category-slug-wpmu-how-to-make-it-work-with-last-wpmu-30

I switched this to off and the category slug field reappears. If anyone can comment on whether its safe to switch this off, that would be greatly appreciated.

error code: 523