I agree Amazon have been a let down regarding this game. From experience I've never had problems with them.
To be fair, Amazon is massive and stocks hundreds and thousands types of items and they have various warehouses across the country. For releasing games, the gaming retailers will always be better at meeting release dates and have more information about the product as that's what they're entirely focused on.
I've just got dispatch email from Amazon and they did promise for it to be delivered today, in one sense, yes I'm annoyed but does waiting an extra day or two really make a difference for me? the answer is no. On this occasion, I'll give them the benefit of doubt.