The tram is incredibly useful if you're staying at Mandalay Bay and want to hang out at NYNY (just across the footbridge from Excalibur).
However, the hours are ridiculous. Stops running at 10:30pm on a Friday night? This is Vegas! Luckily, the footpath between Mandalay Bay-Luxor-Excalibur was built before all the trams/trains/taxis and is fairly easy to follow. It's just not as FUN as the tram!