Well, I've learnt shitloads since coming here. That's a change in the state of my knowledge; I can't complain about that.
I'm better able to debate and put forwards arguments.
I've become an agnostic where as before I was an out and out atheist. That's a really big change, I reckon.
It's also fun; I like arguing and trying to put a good argument across. The fact that people stay here for years shows that people do get reward from being here.
Is it pointless? By what measure? Talking with one poster helped me improve my professional practice. That is certainly not pointless.