Ah, at last, the nightly builds of Firefox have been fixed to allow for middle mouse click in OS X. It's good to see this 2+ year old Mozilla issue finally resolved, and I'm sure my friends on IRC will be glad as well - every few months, I'd point out how pissed off the bug made me.
Thanks go to the guys who put the effort into this, I'm really glad to have my favorite browser working properly in OS X.