Well, I only started getting back into watches around November/December last year...
So for the trips I've gone on, I always take a Timex that I can use in a sauna/jacuzzi/swimming.
Copenhagen, Denmark (Dec/Jan 2006) - PT YachtMaster
Vilnius, Lithuania (July 2006) - Silix PAM036 and MBW Two Tone Silver Serti Submariner
Stockholm, Sweden (October 2006) - Silix PAM036, EL PAM092 (for fitmic) and gen. titanium Omega SMP Chrono.
No problems anywhere, though they had a look at them as I took them off for the x-ray machine in Lithuania. Nothing was said, but they checked my TDK CD case with built-in speaker, but it was ok in the end.
I usually go wearing a watch on each wrist, and the timex (on the last two trips) was in the suitcase. I also take around 5 watch straps for the PAM, but put the screw drivers in the suitcase. My view is if I lose the suitcase at least I havent lost the watches or the straps.
This week, coming back from Sweden, I found that the handle on the suitcase was broken - the baggage handlers probably threw it on and broke it in the process It was not convenient getting back home on the train with the suitcase in that condition.