Improving user-perceived performance and responsiveness is definitely a priority for us. We now have a team dedicated to tracking down FirefoxOS performance issues, and we have been standing up automated systems which can measure this sort of thing on an ongoing basis (e.g. my project, a camera-based system which draws data directly from user-perceived output: http://eideticker.mozilla.org/ and http://eideticker.mozilla.org/b2g).
If you're interested in learning more about our efforts, probably the best place to start is the FxOS performance team's wiki page:
Posted Sep 5, 2013 22:58 UTC (Thu) by liam (subscriber, #84133)
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Thanks for the eideticker effort. I hadn't heard of that.
I've subscribed to several key performance related bugs already but haven't seen much movement with them.
What's more worrying is that there doesn't seem to be much talk about improving responsiveness. Originally the goal was to perform better than android with lower-end hardware but that effort seems to have been tossed aside.
Lastly, there is the whole design issue, which corbet was kind enough to delve into a bit in the review.