Yes - I think "interesting" is the right word here. To me it somehow looks like a mix of elements of Windows Phone, Android but also iOS - But I welcome the idea of having a html5-friendy mobile ecosystem, even if the design is yet questionable.
Virtually all Firefox OS apps should also run on Android (maybe with a trivial wrapper), but Android apps will not run on Firefox OS. This sounds like a problem for developer adoption.
I would also say that building Web apps is easier only if you don't care about the resulting quality (e.g. buttery smoothness).
I guess, at any rate, it's good to have some more competition in the mobile space.