I've had some experience with Google Docs, but haven't actually created a survey and evaluated the results. There are a couple of staff members in my building that are very savvy with creating surveys and sending them out to staff in order to gather information for various reasons. The forms are incredibly easy to use and the data is automatically organized in a number of useful ways. I have also filled out surveys using survey monkey, but chose to create a form using Google Docs since it is widely used within my building.
Click here to view the survey I created for my elective class
Click here to view the survey I created for my elective class