Since the session videos will be online after the conference for registered Apple developers (that's what they did last year - setting a new Google I/O-pressured precedent), I think that leaves the sessions you really want to go to, Labs, networking, socializing.
The sessions. All of them are top-notch. Learn how to write code like an Apple engineer or think like one. They all know how to present and they all are happy to be there.
The Labs are unbelievable. You come with your thorniest bug/problem to the appropriate section and an Apple engineer will sit down with you to figure it out. You might have to wait a while but they will bring in other team members, if you have a particularly thorny issue.
When it comes to networking/socializing - just waiting in line for sessions/talking to people next to me - I met people who had written top-selling iPad/iPhone and/or well-known apps.
Oh, and partying. That is almost like networking but with full bar service.
Good luck and congratulations to those going, it's like no other technical conference.
I don't know how long PDC has been doing this, but if it's quite a while now and Apple ignored them the whole time, then that makes it more likely that Google is the one putting pressure on Apple.
To that same note, I think there's probably quite a few developers (like myself) that were quite used to session videos from Microsoft conferences, that the lack of them when switching to Apple dev seemed like a big loss.
Perhaps they helped push Apple that way but as someone who went to WWDC10 with the expectation that I would unable to see the content otherwise as the videos were restricted to attendees (and or those who had an ADC Select/Premier account) it was kind of a shock they went that way finally. Especially because it was announced barely after the conference had exponentially faded from our memories.
Google I/O is pushing the boundaries of free again - live streaming to locally-organized developer parties in select Worldwide locations of major sessions and the keynotes.
The sessions. All of them are top-notch. Learn how to write code like an Apple engineer or think like one. They all know how to present and they all are happy to be there.
The Labs are unbelievable. You come with your thorniest bug/problem to the appropriate section and an Apple engineer will sit down with you to figure it out. You might have to wait a while but they will bring in other team members, if you have a particularly thorny issue.
When it comes to networking/socializing - just waiting in line for sessions/talking to people next to me - I met people who had written top-selling iPad/iPhone and/or well-known apps.
Oh, and partying. That is almost like networking but with full bar service.
Good luck and congratulations to those going, it's like no other technical conference.