Sure, I've been to four alt.polycons and enjoyed them. But there, I actually knew some of the people... and those I didn't, many of them I knew from their online personas. And APCs are *much* smaller, more intimate activities. As well as the program panels usually being things relevant to my life...

Still, APCs also tend to be "geek fixes", given the Usenet group demographics. That aspect of SF cons makes more sense to me now.