(Mozilla developer speaking) I've tested FirefoxOS builds for more "high-end" devices (in quotes, because it is nothing like my Galaxy Nexus and your Nexus 4),

(Mozilla developer speaking) I've tested FirefoxOS builds for more "high-end" devices (in quotes, because it is nothing like my Galaxy Nexus and your Nexus 4), namely the Geeksphone Peak and the Nexus S (a guy in my office is doing the port on his spare time, so I could play with it for a bit). In terms of scrolling/panning/zooming, say, in a list, in the browser or on the home screen, the phone is basically at 60fps the time, the only slowdown I found were some GC pauses from time to time when doing some weird stuff (opening/closing apps like crazy to stress test the thing, basically, could slow the phone down) or browsing heavy webpages (in terms of js and CSS). From dual core and up, the phone is really nice (I personally found the Geeksphone Keon to be too low in terms of specs, the experience was too far from my Android 4.2 device). Apps are coming (I would not have bet on a decent app map, but Nokia's solution is very decent, tbh, altough we certainly need more than a nice map app), hopefully we have something to announce later this year (I don't work on FirefoxOS specifically, I know as much as you do). I also know we also started working heavily on supporting hi-dpi devices [1]. [1]: The branch where the hi-dpi work is happening https://github.com/mozilla-b2g/gaia/tree/v1.1.0hd https://github.com/mozilla-b2g/gaia/tree/v1.1.0hd