I think leaving trays in the hallway is gross. I only do that in certain circumstances - like I need to get to bed. In that case, I call and request a pickup so it will be taken sooner.

Walking down a hall strewn with half-eaten food and garbage is disgusting.

...and I had to LOL about leaving a note for another hotel guest about it. If I had received said note, it would have gone straight to passiveaggressivenotes.com