Long time lurker on flyertalk. I finally think I have something of substance to add. I have GE. On certain trips I buy art -- all over 100 years old, not for resale. I came back from a trip where I bought some things -- some already framed. I came through Terminal 1 at JFK and the set up had changed since I last flew through there. I had more than the $800 and some food, all declared and I wrote a list. First customs guy looked it over and said fine and kept it along with my GE slip and waved me and my baggage through. A second person stopped me and directed me over to the dreaded steel tables. Now I did have a lot of luggage because of the art. I was asked how much I spent. I could not remember exactly what I gave the other guy as I had written it out the day before with the receipts. So I over estimated. The customs person took out one of the blue forms and had me write the number and sign my name and emphasized the importance of me signing the document. I was asked if I was carrying over $10,000 in cash -- I said no, was asked how I paid, and I said card. I offered to show receipts but no, it was inspection time. The agent made some small talk which was an obvious attempt to be friendly but also to distract me. My carry ons and art bag were searched. I was about to open the checked suitcase but was told I could go.
As many have pointed out it is the accuracy of the declaration that is of importance, especially for GE. That was what was emphasized to me when I was asked to sign a declaration on the total amount spent right in front of the agent. Art over 100 years old is not subject to duty so I had no worry about the inspection, and there was nothing problematic. I err on the side of caution as GE has saved me a lot of time and I do not want to lose it.
I have gone through checks before when bringing in art but this was the first time I was asked to sign the blue customs form in front of an officer.