I went to WWDC in 2010, and it was good, but looking back, it wasn't invaluable.
Last year I kept debating whether to go but it sold out before I even was awake, and this year I wasn't going to even try.
People like Marco who went to WWDC for years before the iPhone came out have a very different experience. It was smaller, and they got to know each other and have connections. I had the same thing for the far-smaller SIC conference back on Windows. You'd see the same people year after year, catching up and re-making connections.
By the time I got to WWDC, it was massive. I didn't even see people from Seattle that I knew were there. There's a different vibe for newcomers, with so many people it's hard to really meet anyone. Even if you do, you're lucky to bump into them again in the crowds.
I far preferred the Tech Talk that was in Seattle. Much smaller, and thanks to finding out about the NSCoder Night and Seattle XCoders, I've been able to really connect with other developers.
Hopefully they have it here again and send me an invitation!