I LUV "posted placards" but they too tend to get ignored, just like PAs do.
And 'wheels out' on -300 and -500 series aircraft just doesn't seem to work as well with the 22" rollerbags unless you can get a little elevation under it - as in the pillow trick.
I am all for being able to cram more bags into overhead bins, and I have spent many of a boarding making PAs trying to maximize our limited bin space, and breaking fingernails reshuffling your stuff, but don't forget those bins have to close AND lock.
Funny thing is that I know that I work harder during boarding and deplaning then I do Inflight.
"Would you like more peanuts?"