Firm Conviction - Worth it?

[Teakwood]

From doing the THM guild quests I already nearly have enough marks to buy it, and I'm not terribly excited about any of the other abilities (at least, all the other ones /seem/ pretty much useless) -

Unfortunately the wiki doesn't actually say anything about how useful Firm Conviction is. Does anyone have any relevant data or anecdotal evidence they'd like to share?

Thanks!

[Coglin]

I can't tell the difference.......It used to be great, then they nerfed it to oblivion. I would buy it though. Its too easy to buy all the avaliable abilities that your going to have it sometime anyway, then you will use it just because it is there.

[PanTone]

Absolutely worth picking up.