I went last year and met several interesting people in our MacDev group. Apple also hosts a bash on their campus mid-week, which I didn't attend since I didn't relish the idea of driving down the 101 from San Francisco to Cupertino and back just to get a chance to shop in the Apple company store. The day after the party, I found out that Apple provided buses... Doh! This year, the bash will be walking distance from Moscone, so I'm going.
I imagine that there will be some interesting product announcements at WWDC; certainly the already revealed iPhone will only be 2 weeks from shipping, but I'm hoping that there are some finalized screen shots of Leopard. At WWDC 2006, they showed some Leopard features, but specifically mentioned that the UI was not final "to prevent copying"... I'm guessing that the current generation of Macbooks and iPods are getting close to a refresh, and the Mac Pro towers could use a smaller form factor.