We stayed at the Cosmo for 3 days - really cool hotel. Since the Cosmo is managed by Marriott, we used my husband's points to pay for the room - much nicer than staying at a regular Marriott!
The room was spacious with everything controlled through the TV including the lights! The room was clean and we had plenty of towels so perhaps they have worked through some of the issues other Yelpers have noted.
My only complaint is that the Marquee is very, very loud both day and night. Fortunately, they are closed on Sunday night and it rained on Monday night so we had only one night of the music to listen to. Fortunately we were dead tired from our flights to Vegas so I slept through most of it but next trip, we'll ask for a room on the other side of the property.
I was less impressed with the casino - it's small, dark and very smoky. I play video poker and had to search to find a machine. If you are a big gambler, the Cosmo is not where you are going to want to spend your time.