The idea that a 0.9% increase compared to a 1.4% increase the previous month is a "stall" is the same mentality that says earning $26million in profit one year versus $27million in profit the year before is a loss... it's a common business foolishness that tries to pretend that making less profit is a good reason to cut jobs. As long as Firefox usage grows at a measurable rate, even if it's less than it grew before, it's still growth and shows that people are using it more.
P.S. My sincerest apologies to any corporate executive types who read my previous paragraph and got their feelings hurt. Ha!