Invitations by Dawn is having a sale on wedding invites right now and I came across these seal and send invites. It's an interesting concept. They feature a perforated response card printed with your return address on one side and your response wording on the other. Guests fill out the card, remove it and return it to you. You can also include info like wedding website and registry on the card - its essentially one long card that folds up neatly into the envelope without having to use inserts. Has anyone used anything like this? Thoughts? Opinions?