I agree with everything Mike said!
Having been a manager for many years, we were required to be in constant contact with our employees so we know how they performed. We were also required to give them feedback on a regular basis so both they and we knew exactly where on that 1 to 5 scale they were performing. So when it came time for semi-annual counseling sessions and annual performance reviews, there were really no surprises. I always hated supervisors who never discussed anything with their employees during the entire year and then when the annual performance reviews came around, they would drop bombshells on unsuspecting employees.
The survey results do provide some feedback to management as to how the passengers feel the staff is performing. It may not be a perfect solution, but each employee does have a certain level of 'guest satisfaction' that they're required to meet. Let's say they are required to have at least a 90% satisfaction rating; if they meet or exceed that, then they are performing their job adequately, whereas if they fall below that, then there are problems that need to be addressed.
In this industry, at least for the most part, it's 100% service oriented and the feedback from the passengers is one way to help determine how well they are performing their jobs. But it should not be the only way. Keep in mind that most people expect good service and if they get it, they don't say anything. But if one thing goes wrong, then they complain. And of course as we all know, if one thing goes wrong, then some people will then start complaining about everything else.
As I use to say when I was a supervisor in a service-oriented industry that it's almost like we don't rate performance on positive feedback, because we never get any. But instead we have to rate performance based on the the lack of negative feedback. If we don't get any negative feedback, then we know they're doing a very good job.
Personally, I think it's important to give fair and honest feedback if the service was above or below what is expected. Of course, as was stated, expectation can be skewed based on a person's past experiences. While one person feels it exceed expectations, another will feel it fell below expectations.
But with all that said, I do know management reads and pays attention to the written comments passengers make. So, if you feel everything was fine, whether you submit the survey or not is fine. But if you feel there was something either above or below your satisfaction, then you should not hesitate to submit comments.