We've seen a few different viewpoints when it comes to Android fragmentation. Nick Bradbury, for example, says it's not really a problem, while Danny Roa says it is a problem, but everybody should just stop worrying so much about it. But fragmentation isn't only an issue when it comes to the actual functionality of Android apps; design is a concern as well. That's what Kirill Grouchnikov explores in this recent Google+ post: how to handle the fragmentation of Android's look.
Grouchnikov provides two apps as examples: one has a familiar Gingerbread look - "very dark slightly translucent background and light grey button bar," Grouchnikov says - while the other has a more up-to-date look. The problem is not so easily solved, though, says Grouchnikov:
Should you be bringing the ICS/JB/KK styling of buttons, checkboxes, radio buttons, sliders, spinners or scroll bars down to older platforms? Once again, that depends. You can see the Play Store doing it, for example, with some of the spinners (search for something and look at the selector at the top). But there's only so much you can do at that level without really deviating from what the user is accustomed to seeing in other apps on the device. And there's only so far you can get to dig yourself out of the uncanny valley where the controls look and behave almost right, but not exactly right.
So, maybe Android fragmentation is a big issue, maybe it's not, but this is definitely an important consideration: who are your users, exactly? When they open an app, what do they expect to see? Check out Grouchnikov's full article for the rest of his thoughts on visual fragmentation.