My wife and I were toying with the idea of driving from coast to coast (SF to NYC) with a rented car this June.
I just applied for a travel authorization via the ESTA web site, simply left the yet unknown details (flight number and such) blank, and both applications were instantaneously approved.
Now I find it a bit irritating that the approval notice reads: This does not guarantee admission to the United States; a Customs and Border Protection (CBP) officer will have the final determination.
The final determination?? Taken at face value, this would mean that our actual admission is determined not necessarily by law and order, rules and regulations, but if I'm unlucky, it depends on the inscrutable whims of one self-important government official, who has the authority to send us back without reason
Needless to say, this would entail a very significant financial risk, since so many things would have been booked in advance
[ Edit: Edited on 28-Jan-2012, at 12:52 by Rainer Dynszis ]