I have ridden this tram twice--once when City Center first opened and yesterday to go from the Bellagio to the Monte Carlo while avoiding the heat of walking the Strip or going the meandering way through the hotels to get to the MC.
The tram is efficient and it's air conditioned. I saved quite a few steps and go to and from the Bellagio - Monte Carlo with a minimum of stress.
There is no charge to ride the tram. It's great for visitors but for me, I generally park at the property at which I want to be and walk the short distance to a neighboring one.