You get Rajasthani food all over Jaipur but the I can assure you that you will not get to experience the ambiance anywhere else.
To dine in Ajmer Mahal, on the rooftop, under the twinkling sky with a breathtaking view of the city is something I dont mind paying for even though it burnt a hole in my pocket. ;)
Firstly, go there for the ambiance and then for their Royal thali. The thali has so many dishes that you will not be able to finish it. It is not only filling but hugely satisfying.
Staff is extremely courteous and make sure you are comfortable with the food as well as seating. The ambiance and decor is princely.
It is a must visit place and you will have an awesome experience.