On the other hand it's a dev preview, not something designed to be used by high end customers.
Right now, Firefox OS is extremely far back in line. It's behind Android, iOS, various mobile versions of Windows, BlackBerry OS, Symbian, MeeGo, and several others.
If it offered something special, then there's the remote possibility that it could succeed. But it really doesn't. It's quite unremarkable, and the emphasis on using HTML5 and JavaScript for app development will likely repulse many good developers who'd prefer to use a language like C, C++, Java or Objective-C.
It just keeps looking more and more like a dead end, even as they make progress.
But it will attract developers who use HTML5 and Javascript, of which there are a great number.
FirefoxOS is clearly aiming itself at low-end devices in emerging markets. None of the other players have done a great job here, so yes, there is a market. We're just not in it.
Like it or not, the core of the idea is using web technologies. And there are good developers who like this. After all, you can use the same mix of skills to make the website as the mobile app.
If you want to write apps in Java or Objective-C, there are already platforms for that. Firefox OS will not get extra traction by being an inferior version of those platforms.