This would be a very useful feature for me also, but the result of populating a user field with "yes" or "no" doesn't really yield the results I would like.
I need to be able to run a simple report or have an Email sent to me with the results in i.e. a list of all those who have clicked the "yes" button and all those who clicked the "no" button. Anyone else can be deduced as a non responder and can be disregarded.
Is this possible? I guess I could use this method to subscribe to a list but that has drawbacks. Firstly, I would need to create the list, secondly it would need to clear down each week or be deleted automatically, thirdly, a list of subscribers doesn't really fit the bill.