Short version: 65%
Katy and Bob is hardly an innovation in the diner dash type time manager genre, but it is easy, lasts fairly long, and provides enough fun to justify its price.
Long version:
Katy and Bob: Way Back Home is a standard Diner Dash/Delicious clone, where we play as two spoiled rich kids stranded on an island by their father, so they can learn a lesson of self-reliance. This is pretty much the entire plot, but these games were never famous for their storylines.
Since we run a bar instead of a restaurant, we do not have to worry about seating, only customer temperaments and the large variety of things they can order—cocktails, juice, ice cream, and so on, all with an assortment of dressings. Furthermore, there is a small tycoon-like layer, where we can buy upgrades for our characters (these are permanent) and for the bar as well (these reset every 20 stages).
Despite this complexity, Katy and Bob remains casual level game. Some of the 60 stages may need preparations in bar upgrades, the timer can be a bit tight, but it is also easy to keep customers perpetually happy by chaining long combos together, even if we have to make them wait beforehand. This trick can make stages repetitive, but it is part of the genre anyway, so if you enjoy dash games, you will definitely like Katy and Bob.