SXSW is a very efficient place to go if you stick to the sidelines, hang out at a nearby coffeeshop and do work. You end up meeting more people that way, seeing familiar faces, and getting more done. Every year I've been there I've gotten things done more quickly (business deals, press meetings, customer feedback) simply because of the sheer volume of people there.
The key is to pick a spot to camp out at, and invite people to meet you there. It creates stability and easy collaboration. I am always surprised by the new and old people I run into there. Easier than spending a week or month going back and forth on E-mails trying to meet.
Allowing serendipity to run it's course is quite efficient. The creativity comes from the conversations and living knowledge in small groups and hangout sessions vs. the panels and the ads. There are many layers to big events like this.