IMO it isn't a complete mess. Yes there is fragmentation but that doesn't mean it is a mess and there is fragmentation elsewhere too...An iOS device may get put on the most current version of the OS but likely you won't get all the features of the new OS unless you upgrade to the newest device
take Siri for example only available on 1 device and it was the "big" thing Apple hyped for the 4s because it doesn't work on the 4 or 3GS...
