The people who point out "90% of Apple iPhone users are on the latest OS version! Android sucks because not everyone is on the latest OS!" don't realize (or care) that Apple just bundles up a bunch of userland components and calls it an OS update. Nearly everything but the kernel is auto-updated to the latest version on all Android devices, even if they're several OS versions behind.
The discussion should be around "What is it that people without the latest hardware / OS version can't do?" not "What number does your phone say under OS version?"