It's a nice and well designed game for how small it is, both visually and mechanically. I don't know how some others here are saying it's 'relaxing' because I was stressing out trying to get the latte orders done, I actually preferred the late night customers more for their simple orders.
If I had to be nitpicky, I would just point out that it's possible that customers can leave the queue before it's possible to finish their order, that being said, the game doesn't really penalize you for failing orders, so it seems okay.