I'm glad you brought this up because I've always wondered why I said and heard "use to" without the "D". ever since I was a little kid I have never uttered this phrase with the "D" pronounced. I think it just naturally disappears. It wasn't until I started seeing the "D" in print and wondered about it, years later, that I even questioned the incorrectness, grammatically, of "use to". But, to my ear, and because I became use to hearing and saying it, it *sounded correct to me. I was never comfortable saying or envisioning the "D" there. I'm still not, even though I know it's supposed to be there. In short, I got use to use to instead of used to used to (or somethin' like that). You see, as Guy de Maupassant once said, "'tis all a muddle."