As a member of ground staff, I was standing by one of our GB Airways Boeing 737's (was it really a long time ago!) idly watching the passengers disembarking when I noticed that the window immediately behind the door looked wrong - slightly askew. I alerted an engineer who had arrived to "look at something on the flight deck" who promptly diagnosed that a window seal had gone and the window glass had shifted a bit.
He said that I was quite right to point it out because changing a seal now and resetting the glass would possibly save a decompression at some point - a situation which isn't likely to kill anyone if they follow the laid down procedures, but is nevertheless a very frightening experience.
So, yes, if you fly often and you know the usual looks, smells and sounds you experience around aeroplanes and your brain tells you there's something strange, it doesn't do any harm to let a crew member know.