For a given method of transport to become the most popular, it needs to be the safest, cheapest, most efficient way to get from point A to point B, relative to comparable forms of transportation. In this case, the comparable transportation method is to use normal trains, which run on coal, electricity, etc.
Let's compare the two:
This is sort of hard to compare because the two methods involve different ways of killing people. There are the old "run-someone-over" and "hit-a-service-vehicle" scenarios, and in fact the only major (and fatal) accident on a maglev train occurred about eight and a half years ago. 23 people died when the train hit a service vehicle. However, the crash was attributed to human error, not the maglev technology.
Putting these types of accidents aside, maglev trains aren't any more dangerous that normal trains. People can die if they accidentally touch power lines, but normal electric trains pose the same risks. Fires aren't any more likely to be started, and fuel can't be spilled. So safety isn't an issue.
Here, there is a difference. In a Congressional report, Report to Congress: Costs and Benefits of Magnetic Levitation, it was estimated that maglev tracks would cost 40-100 million dollars per mile, compared to 10 million dollars for high-speed rail (HSR). The cost can vary given the area the train is passing through. The report estimates that a maglev system would cost 1.92 times as much as an HSR system in rural areas, 1.22 times as much in suburban areas, 1.20 times as much in mountainous areas, and 1.13 times as much in urban areas.
That's very interesting, because it shows that the technology might be accepted in some areas but not others. Maglev subway systems and elevated railways could become more prevalent in cities but not in rural areas. It wouldn't take too much of a change in infrastructure.
Different routes lead to different costs per mile, with the cost of routes in the American Northeast Corridor being one and a half times as much as average. Fortunately, thus setup is an outlier, and is really due to the high population in the region and the replacement of the existing rail lines.
Different methods range in price, too. The Congressional report also compares the programs of different countries. They vary quite a lot, though, and there doesn't seem to be a definite pattern.
One last thing: The report was written in 2005. Since then, the value of the dollar has changed and technology has improved. I think that the cost of maglev trains has gone down quite a lot since then.
This paper (admittedly short) compares a German Transrapid maglev train and the ICE 3 high-speed train, also developed in Germany. The energy usage is about the same, though at lower speeds Transrapid has the edge over ICE 3. There isn't data for higher speeds, though, which is odd, because the newest Transrapid models can go much faster than the data explains.
This article shows that maglev trains are still many times more efficient than airplanes or cars. It's also a bit speculative (using maglev as a launch system for spacecraft?!), but it's fairly comprehensive. But it's a bit dated, like the Congressional report.