While the board mechanics mentioned in the linked article are fun and interesting, there is little variation in gameplay style from level-to-level, and as a result, PAD is grindy as hell and is the reason I've stopped playing. A modern freemium mechanic other apps use to combat player dropoff for this reason is Auto play, which lets the game play itself (or simulate a runthrough of a round) for the same rewards. There's been a lot of debate in the gaming community on whether this is good design, but Star Wars: Galaxy of Heroes, a F2P game which implements both styles of Autoplay, has been doing very well on the Top Grossing charts.
Acording to a recent estimate, something like 0.19 % (https://news.ycombinator.com/item?id=11354546), and given the type of f2p under discussion, "the autoplayers", that fraction should be compared to something like the the rate of gambling disorders in the US population (around 1% for adults, 6-9% for youngsters http://www.ncrg.org/sites/default/files/oec/pdfs/ncrg_fact_s...)
I also attended a talk in Tokyo by the designer of Puzzle & Dragons who pointed out he considered it an action game. It was specifically designed to require you to move fast. Since you can manipulate the entire board in a single move but you have a limited amount of time to do it the faster and more accurately you can move a piece the better you do at the game making it an action skill based game, not a typical pick 3 game.
Yes I realize that partly what the article is about.
