It depends on the current state of the project I guess. It might be quite important that your visitors quickly spot the feedback-button when they have not yet d

It depends on the current state of the project I guess. It might be quite important that your visitors quickly spot the feedback-button when they have not yet discovered the full value of the service provided, IE when there's no incitement for them to scan for a way to send feedback. In a later stage when feedback from users -- as opposed to visitors -- is more important the feedback-button could move down into the footer instead to make other calls-to-action more prominent. Having that said, I'm also a little allergic to these feedback-buttons.