Count me among the grumpy dinosaurs if you wish, but I'll sit out this event. Penpa is fairly good for what it is, but it's still very far from solving on paper from a user experience perspective. It probably took me a while to learn when I was a little kid, but by now I'm quite adept at using paper and pencil, and that is a very very high bar for any kind of user interface to compete against (largely because of another equally amazing piece of technology: the eraser). Penpa has a learning curve, not an unreasonably steep one from what I can tell, but for me it just kills the enjoyment of the puzzle to not be able to just draw harder/lighter lines by pressing harder/less hard on my screen, and quickly erase the lighter lines. (I'm sure there are features to do something equivalent, but they require navigating a user interface.)
Also, on the second practice puzzle, Penpa let me put stuff into the grayed area and it wasn't clear (until I counted and convinced myself it couldn't be) whether that region was meant to be part of the puzzle or not. (I guess that's why there are practice puzzles at the start, so people who will be doing this seriously can figure out how to live with Penpa.)