New Zealand Post launched a similar service in November 2012 and I use it almost extensively now for all USA purchases, as it has been in most causes cheaper to pay for USA to USA postage and then USA to New Zealand, than direct.

However the 'base fee' for the New Zealand version is 1/2 the cost of this, and the 500g is is a few dollars cheaper - minimum cost is $17.25 + they also offer a multiple parcel discount of $6

True consolidated shipping is also coming soon.

Never used it for Amazon or HTS parcels you can't be sure that those stores will use a small outbox or spilt the shipment