Trust Certificates and Seals

I recently came across a site called Link hidden: Login to view that talks a lot about how trust certificates can really increase your sales. I have a friend that really upped his sales when he added seals to his site. I'm just wondering what kind of experience anyone else has had. Please - only those that have tried them.

personally, if your selling on Ebay, its a dog fight anyway....and you always have the good old Paypal, if your selling from your own site its worth while