My hubby and I have been playing Hay Day for about a year. It has been in the top 5 in the iTunes store ever since....and no....not because we have been spending tons of money...

What I like is they make it easy to get diamonds (greenies in Airport City) so since initially spending a few bucks to get us started, we haven't had to buy anymore. Not like Airport City where they are hard to come by and since you can only get to level 40, they don't give you anymore for levelling up. From what I can see, there is no limit in Hay Day.
It is a cute game, you feed animals, milk cows to make cheese, butter etc., collect eggs from chickens for baking, shear sheep to make sweaters, grow crops, fish, fill boats for delivery etc. Right now the farm animals are dressed in halloween costumes. They have a catalogue filled with hundreds of items from other players you can buy to help your farm out or sell to help others, so it is very interactive and you don't have to be friends with any of them. You can choose random people to be your friends and invite facebook or game centre friends to join.