Even though MGM Signature is connected to the MGM Grand by a walkway, it truly feels like you are at a different resort. The Signature doesn't have a casino in it, which was nice. Each of the three towers has their own private swimming pool. There is a Starbucks in Tower 1 and this awesome cafe called Delight (with healthy options) in Tower 2.
The rooms were clean and quiet. We stayed in a suite which had two bathrooms, a foldout queen couch, and enough space for an air mattress. The appliances are all brand-new in the kitchen and we also had silverware, plates, etc.
My only concern was that the water was very hot in the shower and sinks. It had to have been way above the recommended 120F (safety concern). Other than that, it's a good place to stay.