It depends on what you're trying to get out of it IMO. If you're looking for early-stage active feedback on your site I would have to suggest my own app, http:

It depends on what you're trying to get out of it IMO. If you're looking for early-stage active feedback on your site I would have to suggest my own app, http://www.launchly.com http://www.launchly.com. If you're looking for more passive/general/long-term feedback, idea, or problem reporting, then I would say the top contenders in that arena are getsatisfaction (which I use on launchly), uservoice, and kampyle.