It depends, I usually listen to a couple of talks and go outside to chat to some people. There's also half an hour at the start to just talk to people and eat pizza.
I went to the pub after and it turns into a slightly more one-on-one setting as only 30 people or so will go. I've been going for a year and a bit and it's definitely worth it.
It's a little bit of A, a little bit of B. The start of the night was very much a mingle, networking opportunity before the talks started.
After the talks there was a gathering in the pub around the corner, which I'd of loved to of gone to, but unfortunately the last train home was calling me.