Same here, and that's my experience with flying too. I've checked whether it's OK to fly at things like park offices on occassion, but other than that I don't recall a single instance where I've seen someone official who might have cared while I was flying, either in the UK or overseas. That's not helped by multiple people in the recent hearings acknowledging that the police are only likely to challenge a pilot if they have reason to suspect a breach of the Drone Code - and that's assuming they even recognise a breach when they see one.
I am definitely NOT expecting this to have a high-percentage take-up, especially given the way the CAA and Government hasn't publicised this new requirement so far. Unless the plan is for a media blitz now the site is live, I just don't see how they are going to reach out to all the more casual fliers with drones. Factor in those who feel the risk of getting caught is so low registering is just not worth bothering with, plus that those fully intending to fly illegally definitely won't register, and you don't exactly have a recipe for success, IMHO.