Cheap sanity saver
First thing I'd like to address about this review is that it is actually not required that any money be put into this game. Is it encouraged? Sure. How else would they be able to continue providing entertainment? But never once have I had to put a single dime into this game. I play it for my own relaxation and have beaten nearly 400 levels without paying real money for anything. The coins that you can opt to use (again, still not required although it can make things tremendously easier) can be earned for free. Since all the updates they've made it where you can earn coins simply by watching ads--I know, what kid wants to watch ads, but there's a solution for that!--or by completing certain in game objectives (like beating 3 levels or connecting a certain amount of jellies).
Although only older kids (and adults! ;-) ) will understand the actual gameplay and get full enjoyment out of it, it has been a great sanity saver for me with both my 6 and my 2 year old. It's colorful, it's shiny, and it's attractive. It holds their attention during extended wait times at the DMV or a restaurant after they've lost interest in coloring. It keeps them quiet at least for a few minutes when they're being roudy and rambunctious around the house. Overall I'd say it's been very much worth downloading.