Mozilla wrote in its blog post announcing the simulator add-on that the tool has two complementary goals for helping developers. Currently at version 0.7, the company hopes that by version 1.0 the add-on will be stable enough to let developers easily create apps for the new OS.
The second goal for the add-on is that it frees developers from having a device to install a pre-release build of Firefox OS. Given that the Mozilla has said that the initial target audience of Firefox OS will be emerging markets, this could be a boon for developers who may have limited access to multiple mobile devices. It works via the B2G desktop client, which can't emulate device hardware but does have several non-desktop APIs enabled.
Although Mozilla says that it's not having problems getting developers interested, it's hard to imagine that it's not an uphill struggle as Firefox OS joins a crowded field of mobile operating systems. While Symbian is on its way out, and iOS and Android get the most attention from developers, the new Windows Phone 8 and the upcoming BlackBerry 10 will also be clamoring for developer attentions.