The only way to understand the end-users actual experience is to ask them. You need to identify areas for improvement and subsequently measure if improvement has taken place. A survey is useful to set a benchmark but its only when you do another survey with exactly the same questions to a similar audience that you can measure change. A raw score number is of very limited value without a benchmark.
Questions have to be worded well to take out bias but the most critical point is to ask the same questions each time. Resist the temptation to improve them because it will skew the results when you repeat the survey. The questions will tell you whats wrong but individual comments will tell you why. Its therefore vital to give plenty of room for comments.
If you can do some face to face surveys use them to test out the possible questions. I’ve found that with well worded questionnaires I learn a lot about customer experience. To me the biggest challenge for organisations is to recognise what they have discovered and to take appropriate actions based on those findings. That’s often where outside help can add significant value.
The final point is to ensure that you tell your end users what you have done, or not done, as a result of their feedback. Only about 5% of surveys do this.