yeah that's sort of the shitty thing with android -- you have to really try to cover all your bases, and those bases happen to be over a thousand different devices and instances -- firmware, OS overlays, processing speed, blah blah. Luckily we're not the only ones -- Instagram runs like shit on most androids around 2 years old.
There's an update for the android version that we just pushed about an hour ago, hopefully that makes it run a bit better. it was mostly a performance update.