As already known, the first generation iPad and third-generation iPod touch will not get iOS 6 update. The iDevices that will get the udpate are iPhone 3GS, iPhone 4, iPhone 4S, fourth generation of iPod, iPad 2, and new iPad (third generation).
Although get iOS 6 update, not all devices will have all the features offered on iOS 6. Only devices with A5 or A5X processor (iPhone 4S, iPad 2, and new iPad) can use Flyover and turn-by-turn navigation feature on iOS 6. Apple does n oot give a reason why they don’t give that features on devices with old processor, so the conclusion is because the processor is considered old and not powerful enough to run that features. Moreover, the iPhone 4 can not use FaceTime feature via cellular network.
iOS 6 on the iPhone 3GS will also miss some features such as photo stream, email with VIP contact and flag feature, and offline reading. Because iPhone 3GS was launched three years ago, it is tolerated that some features are not provided by Apple in order to maintain performance.