The surveys are very useful. If you truly want a problem looked at, give the item a very low numerical rating, like zero or 1. Anything above a 4 won't get much attention.
If allowed, describe the problem briefly, no long rant. But it is the low numerical rating that gets assigned to somebody to look into, in my experience. So if you do it, mean it, because you might get a call from someone to ask for more details. I used to hate to complain about something when my stay was comped, but I make sure to tell what is good as well.
BTW, last time at Bellagio Café our favorite server thanks us for his being recognized due to us giving him a good rating and comments on the survey. I think he said he got a bonus and some movie tickets, like employee of the month or something. I was surprised that he was told our name as the source, but he assured us it was. So it can work out well for employees who gives you good service if you praise them. Problem is trying to recall their names after the trip.