Good in theory, but I've seen a non-insignificant number of users marked as green despite repeatedly making multiple obvious anti-trans posts. And vice versa, users marked red despite being vocally pro-trans + trans themselves. That coupled with some of the guidelines on who should be marked green/red make the extension almost worse than useless. (EX: Using the 4chan originated "Theyfab" against others is not enough to flag as transphobic) The extension also leaves little room for intersex people and/or those with contradictory identities, often flagging users as anti-LGBT for simply identifying as intersex/"weird flavor" of nonbinary on their profiles.
Good in theory, less then useless in practice.