I order from amazon all the time.. Maybe once every 2 months.. Shipping cost is a bit freaky but the USD price of books is really low (look at amazon.co.uk and its double) so its swings and roundabouts.
I find they take anything from 4 or even 6 ish weeks.. Cartainly I dont get 7 day delivery (is this a courier upgraded shipping ??) As you dont get much discount on group shipping (some but not much) its better to have a few coming regular and then have a stream of parcels IMO.
I have never paid any duty on purely books. But if you have one DVD in the package the whole bundle can get taxed, I was once told that maps do the same so what happens if you buy an atlas
!!! I also have never had ana amazon box go missing either. Tho now I am out of Patong my post has gone crap and many 'test' letters I have sent myself have not been delivered.