I'm going to start off with sound. These things are quiet! How quiet you ask? Try standing under the monorail track in Future World at Epcot (pictured) and not hearing one until it's right over top of you. This is all due to them being powered by a 600-volt electrical system. The rail it travels on supplies the power to the monorail through a busbar and puts it in motion without the help of a fuel powered engine. This keeps them quiet, and cleaner than a bus or a boat.
Scenery. Now this might not be very important to most people, but I'm the type of person who enjoys being able to see as much as I can while I'm on vacation. No better way to see the Walt Disney World grounds than taking the 14.7 mile monorail trip. In fact it's the only way to get a grand tour of Epcot, the Seven Seas Lagoon, 3 of WDW's 24 resort hotels, and the Magic Kingdom from above without having to take a helicopter ride. Not to shabby for a ride that you can enjoy without having to purchase a park ticket.
The cars. Each of the twelve MK. VI monorails in service (identified as Red, Coral, Orange, Gold, Yellow, Teal, Lime, Green (yes, there's a difference), Blue, Silver, Black, and Peach) has 6 cars that it uses to transport approximately 250,000 passengers daily. Inside of the cars you'll find soft blue seats that fit anywhere from 4-5 people at at time with plenty of standing room to spare. With it's constant gliding (unlike a bus which makes many stops due to traffic and lights) its very comfortable even when standing. Much unlike a NYC subway or Chicago Metra train, you're not going to find piles of dirt and graffiti. The cars are well maintained and stay as clean as the parks (which is another post all in itself).
The spiel. This is something you're not going to find on your average train ride. What exactly is the spiel you ask? An almost familiar voice sounds over speakers inside of the monorail cars to tell you what you're seeing, and other events that may be occurring inside of the parks. Below is a Youtube link containing one of the spiels from the late 90's (Sorry, I keep saying spiel).
Don't forget to stand clear of the door.