Since I fly a lot for my work in the computer industry, I've been placing a roll of Portra 800 and Provia 400F in my carry on bag just to see what happens, of course, my real film is being hand checked. I usually shoot a MacBeth and drop it into the bag the night before I leave.
I had no problems at Logan in December. However, the Portra showed effects after flying back from SeaTac. Both films showed effects after coming back from LAX and Las Vegas.
The films were nuked once in Indianapolis and then once when coming back at the destination airport. Of course, this is 120 film, so with SF, I'm not sure. A friend of mine does the same thing and recently went to Paris. On the way there, he had to get his film x-rayed at JFK and then at DeGall. It was fine. His rolls from when he left Heathrow to JFK, got nuked like hell.
The usual contrast reduction, wavy lines were seen in all the nuked film. In the US, the TSA has rules about hand inspections and you'll always get one (if not, ask for a supervisor and plan on quoting their own rules). Outside the US, you have no rights to hand inspection. If you present yourself as a professional, and don't look like a potential terrorist, you'll probably get one, but don't count on it. The brits are still paranoid of the IRA, it seems.
BTW, if you are planning on taking any flash units, pack the strobes, don't leave them in your carry-on. Even though the TSA people are more knowledgable, they still freak out when they see a Metz through the x-ray machine. Pack your favourite brand of peanuts instead...