I flew from DFW International to New Orleans a year ago, and didn't have a problem. I had all of my TriX 400 in a zip lock baggie, and took it out of my bag when I got to security. I handed it to the woman and requested a hand check, and explained that even though it was ISO400, a build up over multiple trips through the X-RAY could affect it. She gave me a bit of a "what the hell is this guy wasting my time for" look, but hey I was just following their rules. If you are persistent and insist they'll do it.
I did the same on the return trip from New Orleans.
Today's machines may not affect film like they used to, but why endanger your film if there is an alternative? I certainly wouldn't cause a scene, but I wouldn't roll over either.