This was our first time at the Signature and really enjoyed our stay in tower 2. Check-in and check-out was seamless and quick, (being a third party reservation through Airbnb was straightforward) and the process was so much faster than check in lines we observed at many other vegas hotel lobbies. Everyone we interacted with from the front desk, the valet, the bellhops, concierge (tower 1) to the person who came to fix our toilet were very friendly and efficient.

The room was very clean and comfortable, and our daughters deemed the pull out couch comfortable and spacious. We made use of the pools at both the Signature tower 2 and MGM. Make sure to pack a swimsuit cover-up as they are required around the resort.
We purchased a 24hr monorail pass ($12) which we found extremely handy because the station is so close to the Signature - MGM entrance, no need to walk through the smokey casino floor and crowded streets. We really liked that it stopped at Bally's/Paris and the Linq hotel, the locations of some of our favorite eateries/restaurants. We didn't have time to take it further up north but it does run all the way to/near the Stratosphere.
A few things to note:
Give the valet time for retrieving your car. Lots of traffic and long lines of cars in vegas can make the wait upwards of 20minutes. the valet was very apologetic about it and it really wasn't his fault.
Communications of most things are directly through the host, but when we asked at the front desk (Louis and Marie were out of town in a different time zone so communications were a bit delayed), the front desk was very prompt and nice about sending up their "engineer" to fix a clogged toilet. Also, we found a plunger afterwards under the bathroom sink. All toilets we used at the Signature (room and lobby) did not have a strong flush so this may be a common issue?)
All in all a great experience and we would definitely consider a return visit.