I recently did the course work and became Nitrox "Certified", but haven't yet used a tank. Now I'm in Cozumel, doing a week's worth of diving and the outfit I'm with said they have nitrox available, if I want it for $10 more. I'm interested in trying it, but I don't think that I will be able to analyze the air in the tank. I just arrive at the marina, jump on the boat, and they setup my gear, attach the tanks, etc.
My PADI Nitrox course made me scared enough about using enriched air if I cannot check the gas myself, and a buddy back home tells me the guy who runs one of the LDS' had his brother die from bad air in Mexico...
am I being unreasonably paranoid?
Always ... ALWAYS ... check your own gas. period. If you can't do this then don't dive Nitrox. It's that simple.
You don't necessarily need to *own* your own analyzer but you at least need access to one that you trust is calibrated correctly.
R..