Never been, but it sounds like exactly the wrong sort of environment for creativity and productivity. Too many people attend; the communication overhead must be insane.
I can tell you that the folks in Seattle failed to launch last weekend. From what I read, it sounded like there were too many chiefs, and not enough indians (or maybe just too many chiefs). I might have gone, but by the time that I found out about it, the event was sold out. It was therefore a bit galling to hear (later, via the blog) that some large percentage of the attendees were PMs, BizDev, and Marketing types.
Anyway, if you view it as a professional networking event, your expectations will probably be more in line with the reality of the situation.
Is it worth doing?