What does it take to make you complain about a hotel stay?

@BoardingArea
One Mile at a Time- At what point do you complain about a hotel stay?: To start I have a confession to make: I’v… http://t.co/JMMaE4Pp

I’ve only once written a complaint letter to a hotel, and that was due to awful service (at the Crowne Plaza Auckland years ago, for what it’s worth). Yes, I’ve experienced minor hiccups I address at the hotel, like if they don’t honor late check-out, don’t provide upgrades within the terms of the loyalty program, etc. But I really don’t know at what point I should complain about a hotel,