I've stayed at the Doubletree Tucson twice, and each visit was an excellent experience. The hotel is very well maintained, with clean, well appointed rooms. I particularly appreciate their fitness center; the equipment is modern and well taken care of.
I've only dined in the restaurant for breakfast, but the buffet is well stocked, but you can also order from the menu.
The staff are very friendly and go out of their way to make sure your visit is a pleasant one. I highly recommend this hotel.