It will be wonderful until the first time a plunger smashes a car with a family to smithereens because the railgun timing was slightly off due to a voltage irregularity.
There are clearly a lot of details that you have to get perfectly right. However getting them right is an engineering challenge, not a physics challenge, and engineering for safety is something we as a society tend to do pretty well. (As opposed to engineering for cost containment, which we as a society are often horrible at.)
If I saw Elon Musk standing up there with cost projections, I'd be optimistic that they were in the right ballpark. If I saw virtually anyone else there, for a project of this type, I'd be assuming that they missed order of magnitude cost issues.
Our current forms of public transportation are certainly not without risk. A runaway DC metro train killed 9 people a few years back. Maintenance workers are regularly killed on the tracks. Extrapolating from a sample of admittedly just one system, I doubt that this would be any less safe than the high speed rail they are proposing.
If I saw Elon Musk standing up there with cost projections, I'd be optimistic that they were in the right ballpark. If I saw virtually anyone else there, for a project of this type, I'd be assuming that they missed order of magnitude cost issues.