Stayed here in April (2013) . I have been to vegas many times, have stayed at Bally's, Planet Hollywood, Luxor, MGM Skyloft Suites. Stayed here from a sun - wed. I came here with my wife and my two children ages 3 and 1 as well as my parents.
Rooms :We had two rooms side by side with a shared entry. First impressions of the rooms were great, clean, well decorated, bathrooms were nice and plenty of sleeping space. Flat screen tv's everywhere and a variety of sitting areas to relax while enjoying floor to ceiling window views. Has a balcony as well.
Pros: Amenities at MGM Hotel are great ( Restaurants, casino, entertainment) , and since you are staying at Signature you have access to all of this. The best amenity for us is the pool complex, quiet enough on the sun-wed so our kids could play, other families there as well.
Best pool complex i've seen so far in Vegas.
Cons : Be prepared to walk. The signature itself only has a small convenience store, starbucks and a lounge area for you to access directly. All the good things are at MGM so although the first few times the walk doesn't seem bad, after a day or two it's tiring. Especially if you want to walk to the strip at night, the trek to the strip although seems close is a few "Vegas blocks".
Overall I would stay here again. For the price, the room that you get is big and emmaculate. Your location is good on the strip and the amenities at MGM are fabulous. One of my top picks for staying in Vegas , especially travelling with family, I would consider staying here with friends as well.