Well, it all depends on how FFOS (Firefox OS) handles the presumably cheap-o hardware. If it is fast, responsive, and handles it well I think the phone will do decently. It would be a good starter phone for kids or teens, or someone who wants to check their email, etc on the go but doesn't want or need a high powered, expensive smart phone.
I think they (ZTE) should port it to bargain networks, like Smart Talk, Boost, Cricket, etc. It may do better there than Verizon/AT&T/Tmobile etc.
I tried the FFOS beta (the browser add-on) and it was definitely interesting to mess around with. Kind of felt like early Android.