We stayed at the MGM Sig in mid-May in Tower 3. We rented through a Las Vegas REMAX realtor who manages about 90 units for owners. She gives some really great rates. Our weekend rate was $119/night (included housekeeping fees) -- a bit higher because it was Country Music Awards weekend.
The room was a Jr. Suite. It was spacious for our family of 4. Only thing is it had a King bed and a sofa bed. There are no Jr. Suites with 2 double/queen beds. So we threw the kids into the sofa bed. The bathroom is enormous, with nice marble and a big shower. The room had a fridge, microwave and a 2-burner stove, toaster, coffee maker, and even a blender. The kitchenette came equipped with 4 table settings. We really had no need for the kitchenette as we ate out for every meal.
There was a flat screen TV in the room and a small TV in the bathroom. We were really happy there. The finishings are high-end and the furniture is new and comfy.
There is a pool and hot tub for each tower. We enjoyed our pool immensely. We did wander over to the MGM Grand pool, as much has been written about its lazy river pool and such. However, we were not impressed. It was busy, crowded with 20-somethings, who were drunk, displayed too much PDA, or were yelling. Not really "family oriented". Also, there were empty beer bottles on the ground, not to mention broken glass. I even saw blood on the pathways. Obviously, some people must have stepped on the broken glass. We high-tailed out of that pool area and returned to our Tower 3 sanctuary and pool.
Negative about the MGM Sig is its location. It is so far down on the strip. We found ourselves wandering to the opposite end almost every day, because we wanted to eat at the Wynn buffet, shop at the Fashion Mall, tour the Venetian, etc. Unless you take the monorail (there's a station at the MGM Grand), any other mode of transportation takes forever to go from one end of the strip to the other.
If you have any questions, just let me know. We loved staying there, but we may consider the Palazzo next time. Not because we didn't like the place, mostly because of its location