I always put all my film in carry-on, as the check-in luggage x-ray machines WILL ruin film. I've gone on trips with up to six passes through carry-on x-ray machines, and film no faster than TXP320, and haven't had any problems yet. Last year I brought 40 sheets of exposed Ektar 100 home from Europe to Australia and they were all fine - all were back in the box and sealed up with sticky tape, with an "exposed film" label (as well as info about how many sheets, and so forth)! Security at Munich were interested in my camera backpack's padding, but not really the camera or the film...
Marc!