Although much cheaper than building a subway or other heavy rail, light rail does little more than busses currently do, aside from the fact that it's on rails, which for some bizarre reason means middle and upper class white people are much more likely to use it....
Cities across the country have jumped on the light rail bandwagon. While they gain something cool to look at (see photos below), they do not gain a viable alternative transportation mode. simply saying, "we need a light rail line" will do nothing to address the fundamental transportation and planning problems present across the United States.
photos of various light rail 'systems' around the country (from lightrail.com)
salt lake city