Part of developing on the Android platform is dealing with the dreaded F word which is FRAGMENTATION.

Its what tech blogs mention when they write about Android. Its the word that scares some developers away from the platform. Its what Apple love to put in a pie chart in their product launches to prove that iOS is the most amazing mobile OS yet.

Personally, Id rather see a Fragmented Android than a Fragmented Mobile OS ecosystem. Its likely that without Android, wed be developing apps for Sony OS, Samsung OS, HTC OS, and so on. I cant imagine that Apple would actually let other companies build phones using iOS.

But still, Fragmentation is a pain. If it can be minimized or eliminated entirely, Id be happier.

Until recently, I was working at Wedding Party ( as an Android Developer. The app was supporting Android version 2.3 and above.

To create consistent UI for all versions, we used the ActionBarSherlock and HoloEverywhere libraries. Animations should be carefully done since one that runs smoothly on 4.x would, more often than not, be sluggish on 2.3.

The Wedding Party app also deals with a lot of images. High-resolution images were out of the question because it uses a lot of resources & using multiple of these images in one screen would almost certainly crash on older devices.

At Google I/O back in May, Jeff Gilfelt started giving away stickers that says minSdkVersion=14. It was a well-received campaign among Android developers that got this conversation started.
More at Danny Roa's Blog