I had the same experience as you. Never used a Cintiq before the job I have had for the last year and half and it has been amazing. I still believe it is just a tool and not to be used to compensate for bad technique but if you have been sketching a lot of you life and you know what your doing it can be a huge productivity boom. All of the feelings you mentioned about not wanting to do the work without on are spot on. But I do think it is worth stressing the importance of learning the hand skills need to really utilize a Cintiq to it potential. It is not a crutch.