As a frequent flier, and aviation enthusiast, and ppruner, I always check flaps/slats whenever I am seated in a place where I can see them. I must say that I would be more inclined to speak out if I noticed something that might be wrong. But then again, I read on the tech log thread that eg an A/300-310 can take off with only slats deployed in certain circumstances...
another thing I always wanted to mention but... I noticed several times, in almost zero wind weather conditions, that IBERIA pilots use lots of rudder inputs during the take-off run, making the plane zigzagging along the runway, (on 767, A320 and MD83) a quite annoying and worrying technique for passengers. Has this something to do with their pilot training?