Using public transportation is very convenient for those patient enough to wait in the cold, but most students carpool for shopping trips. The reliability of the buses is sketchier than that of the Rapid on weekends, but during the week, both are very reliable. The RTA is usually necessary to get to and from the airport in an efficient manner. The trip to the airport on the Rapid is very short, requires no changing of lines and is only about 45 minutes.
Public transportation in major metropolitan areas must remain efficient for the city to remain functional and students, although most are not commuters, the RTA is utilized by students mostly to get downtown to the club district, to sprawl areas with Wal-Mart, Borders, and Cineplexes, and to get to and from the airport. Fares are entirely taken care of with your RTA pass during the school year. Learning the routes, lines, colors, stops, and locations is an entirely other story and may take quite some time, especially if you use only one route (to Walmart usually, and only once or twice a month). RTA staff is usually very friendly and will answer your questions. A few tries and a bit of studying of the routes will provide great freedom if your intent is to venture out of the campus bubble.