I think the interview was just the way they are - bland and boring
but I think they are truly happy. Even though Kate was quite nervous and couldnt do a proper sentence I give her kudos for being authentic, unlike other tacky royal brides who did some bossy talking on engagement day or presented themselves like just coming out of a how-to-deal-with-the-media training. I hope she is allowed to stay herself and I wish them well.
They now have to make the most of the momentum, use the interest and excitement their decision has created to best ability, keep it alive until next summer and beyond. If they do so, there is a good chance especially for Kate that people will warm up quickly. If they dont and go back to Wales to live a quiet life without a proper how-to-involve-Kate-stragety it can quickly backfire, and once the whole "Diana's son is getting married" sugar has gone being out there in the public can be a lonely and unpleasant place if people are disappointed.