Diner Dash has some very interesting ideas for the genre, making it arguably one of the best casual games around. Instead of preparing the food, you have to serve it, and at the speed of light, through multiple commands that, chaining them, give you more points, necessary to finish the level successfully. This is where the game shines. Sometimes you have to serve certain customers first, other times you risk losing the combo or keeping it, etc. Think and act fast basically. With a generally polished difficulty curve, the game becomes quite challenging and addictive, despite how repetitive it can be. Unfortunately it all ends there. The game has some few insufferable difficulty spikes, with literally thousands of customers that won't let you rest, even floating in the entrance or directly appearing off camera from the many that are. It would not be possible to pass these levels if it were not for a broken mechanic... the podium. The podium is possibly the most broken thing you will see in a cooking game. By standing on it after a while, the customers in the queue will become happier. The bad thing about this is that it has no limit, and if you only serve four or five at a time you can keep the whole queue happy and without much effort. This messes up the difficulty the game tries to throw in, for both good and bad reasons. At least in endless mode the podium isn't broken, so you're welcome.
Speaking a little about the graphics and the music, it shows that they put a lot of effort into it, giving the game a unique identity (Flo surprinsingly manages to be a very cool character imo), and the story, which, while... it's dumb (especially in the final phase), has interesting concepts, especially for the genre, which are not so bad.
In short, Diner Dash is a good game, quite polished wherever you look at it, removing certain things like the difficulty spikes, or ignoring how broken it is.
