For what it is, I have to give it 5 stars. Sure, I could have given it 3 or 4 stars because it doesn't go very far. But it's free, air conditioned and goes from Mandalay Bay to Excalibur. From there. It's just a hop skip to MGM or to start a walk on the strip.
There are a few seats but mostly it's SRO. Hold on to the railings. I can really tell who has never taken the subway before. Yes, you can bring alcohol on it.