I'm sitting now enjoying a Bass and a grilled chicken Caesar in the bar at Terminal 7 at JFK airport with a little more than an hour to board a flight to San Francisco. I checked in online and printed out my boarding pass this morning. I've got my Linhof 2x3" Tech V with two lenses, Acratech ballhead, and a laptop in my Urban Disguise 50 bag and my clothes, Linhof Report tripod (the one from the 1950s that folds flat) and other odds and ends in a Victorinox carry-on overnight bag, and no checked bags. The TSA inspectors were interested in my laptop, which got an explosive residue swab, as did the UD50 bag it came in. No problems, and it took me about 10 minutes from arrival at the terminal to arrival at the gate.
I'm carrying just three rolls of 220 to tide me over until I can get to Gasser's, which is a short walk from my hotel.
I'll still check my big series 5 Gitzo when I travel with it, but I think this little travel tripod (about 18-19" long without head) is a good choice as a carryon.
After combing the TSA site for a definitive regulation and finding none, I found a good thread on tripods at flyertalk.com, where some TSA officers participate, and my sense was that the size of the tripod is a factor, so I figured I'd take a chance this trip but leave enough time to check my bag if necessary, or enjoy a Bass if not.