When you have done it once you"ll find it quite straightforward. The paper system was quite difficult not least because the sheets kept blowing away or there was no pen or the writing was illegible. I have used it from scratch following the instructions and once you know where to look for the green light... and if it is flashing it is very visible, it's simple. And, you keep the card on your trolley and use it again and again.
I'm afraid I agree with Mark that the new system seems like overkill and I suspect won't be always used. It also omits two useful features of the old, paper-based system ie the safety aspect of having to sign back in at the end of a cruise and also being able to see who else is currently out cruising; the latter may seem like a minor point, but does in fact greatly enhance the prospects of a convivial and safer cruise in the company of friends.