Generally speaking, I find it irritating, but especially so if I am boarding early in order to snag the overhead space above my seat in a small First class cabin. In any case, in such circumstances I put my headphones on and pretend to read a magazine so that I can ignore them when they try to stop me. It also gives me the opportunity to karate chop the pig that taps me on the shoulder in a laughable attempt to attract my attention as I'm half way down the jetway.