I'm going by gut-instinct and previous Apple shipments. I'll say we'll be in for a surprise and get it end of September. I'll predict the 29th. Obviously I have no inside information, just that Apple has always seemed to be early than the estimated delivery dates.
Traditionally this kind of stuff has always been hit or miss. I would say if it ships early probably will not be by more than a day or so. Though usually I don't believe they're delayed any further. Basically expected around that time. That's still a week or two earlier than I'm expecting mine!