I did not see anything in the user guide about this. 

Is there a way to only allow a user to fill out a form one time, so that the module could be used as a survey tool?  If not, is this something that is on the enhancement list?

Hmmm... Would the user get a message if they went to that page then? I am thinking we could add an event, if the user was signed in you could have an event that gave them a role. The role could be called 'Survey Submission' and the page would be available to users but not viewable to users that have that role? There are a way few ways of implementing this so before we add it to the roadmap I just want to think of all these alternatives...