When I buy a new Ford, one of the first things I do is purchase several extra PATS keys off ebay and get them programmed as soon as possible. Since I keep extra keys for my vehicles in several locations, I generally cut the maximum number of keys allowed by Ford and get it over with.
(IE -- I keep a key for each vehicle at my in-laws house in case I ever lock the keys in the car while I'm there or in case I get locked out somewhere locally so they can just grab the set of keys from their place and come help me out.)
I usually use one of the newly cut keys as my "daily" key, and keep the original factory keys in a safe place so I never run into a situation where I can't easily reprogram a replacement key if I need one.
FWIW -- my local Wal-Mart has always been happy to cut my PATS keys for free on their machine, as long as I understand that if they cut it wrong, it's my problem and not theirs. It's never been a problem, as every key has been cut just fine.