A great breakdown from Matthew Panzarino at The Next Web.
He notes a few places where embracing the natural Android UI works for the app:
The News tab is pretty much the same as well, although there are two large tabs on the Android version, rather than the two buttons of the iOS version. I feel that this makes the ‘Following’ section more visible to users. I know that it took me some time on Instagram before I even noticed that there were two sections here.
He also notes, however, several places where it works against, such as the image capture controls, and the profile screen.
He also points out that the Android app embraces software back buttons, which aren’t usually in place on Android apps due to the platform’s dedicated hardware back button. This goes a little against the grain of what I had said earlier about embracing the native traits of the platform uniformly, but it may not be a terrible design decision; I find that the Android back button is a little too general and overloaded in its functionality. It’s job description is simple; go backwards one “Activity”. However, because this behavior is highly contextual but the point of interaction itself is not adaptable it feels a little janky in all of my experience with Android devices.
Fragmentation rears its head once again with Instagram on Android, forcing the company to leave out features it could have otherwise shipped in order to support the wide array of OS versions and hardware out there. I know people like to pretend this isn’t a problem, but it is.
The app evidently lacks tilt-shift, live filter previewing, and the option to toggle picture frames on and off. From what I’ve dug up, these are features that will eventually make their way in to the app, but at this point Matthew seems to be making the supposition that the exclusion of these features has to do with Android fragmentation. The decision to support older Android devices, and in turn using less powerful development tools and targeting less powerful hardware, can be a hindrance when dealing with apps that do computationally intense things like image processing. So his thoughts have weight, I just don’t know how much.
All in all, it seems like it’s a solid addition to the Android platform, and a winner for the Instagram team.