My personal record for a trip is nine x-ray inspections of my hand baggage over two weeks. Film was all B&W 120 and either ISO100 or ISO400. Eight of the scans were at airports (US, Paris, and Milan) and one was at the entrance to St. Chapelle in Paris. The last was unexpected and I have no idea how their screening machine compares to the airport machines, but I decided to chance it rather than return to the hotel to drop off my film.
The end results: Absolutely no detectable change in the film. No extra fog, no odd marks, no image degradation that I can find. The negatives have the same density range as those I've shot locally.
I'm returning to Europe at the end of the month and I plan to take 35mm this time...I'll let the scanners have their way with my film and we'll see what happens. I won't be worrying about it, though.